So to hopefully settle the matter, here it's broken down for easy ID and also part detail information. Keep in mind, that unlike US made cars, the engine and transmission's serial numbers on the Opel never matched the chassis number. Also be aware of the paradox, where although cars dated August or later belonged to the "next" model year (i.e. a 8/69 manufactured Opel is considered a 1970 US model year Opel), some parts changes occurred at the end of the calendar year (such as, changes in the dash switches happened between December 1971 and January 1972, when the European model year changed). The following is not a complete list, but hopefully enough for owners to know of appropriate components for their Opel GT's.
1968 Opel GT:
Very Rare. The first group of GT's were hand-assembled, and only 31 were produced for 1968 US registration, with most transported to US Buick Dealers for press reviews and early display. With the 1.9 "H" cylinder head (featuring the smaller combustion chamber of the 1.5 cylinder hear combined with the larger 1.9 valves, creating 10% greater compression), these were reported as being screamingly fast. Many unique GT parts were installed in 1968's up until December, but since only a GT produced before August 1968 is considered a true '68, a check of the month and date codes on the back of the dash gauges (use a small mirror) is needed to confirm.
Quick Look Clues:
- "Split" 2-Piece front bumper
- Rear Taillight panel is flat, without the rectangular impression behind license plate.
- 1.9 "H" Cylinder Head marking
- Speedometer face without "W 897" or "w 1062" marking
- Dash gauges have wider chrome ring face
- Air filter lid on carburetor has red part numbers on top
- Spare tire hold down bracket has squared wing nut
- Spare tire wood shelf has access hole for gas tank sender
- Heater valve is located under dash in front of passenger side seat
- Sun Visors are slightly larger and differently shaped
1969 Opel GT:
Big-selling year for the GT, with buyers often having to wait months for delivery. Perhaps more unusual design parts are on the '68-'69 GT's than any of the later years, with some that are not easily interchangeable. A unique "brown" tan colored interior was offered with a forest green exterior for only '68-'69. Another color combination was a red interior with a silver exterior, which is now rarely seen as that color paint faded quickly and was often replaced. 1969 Opels were frequently junked in California in the 1980's, as the clumsy horsepower-robbing "A.I.R. "smog" system was required to be fully operational for state vehicle registration.
(Chassis Number starts with #94-1535504)
Quick Look Clues:
- Rectangular dash indicator lenses on dash face plate
- Button on end of turn signal stalk on steering column
- Lower window crank handle position on driver's side door
- Shoulder belt mounted just below side quarter window
- A.I.R. emissions system on passenger side of engine (pump, hoses, etc.)
- Larger temperature sender on thermostat housing
- Single retainer bracket on underside of hood
- Wiper arm on driver's side without metal "wing"
- Suspension parts narrower: Inner tie rods, Cross Member
- Steering Coupler under dash has metal flex plates (not rubber)
- Headlight mechanism on passenger side has additional micro switch
- Throttle rod is shorter on driver's side of engine
- Ashtray lid is hinged with vinyl cover
- Cigarette lighter and dash mount is narrower
- Headlight lever is thinner, squared-off plastic
- Carpet piece under parking brake handle
- Window regulator pulley is wider than later models
- Car jack has spherical "ball" red handle
1970 Opel GT:
Due to large sales demand and changing government regulations, delays and confusion marked the 1969-70 model year change. Many cars produced with 1969 components were held back for a smog-system retrofit and then sold as 1970 GT's. Significant changes to the manual transmission and rear axle occurred at the end of the '70 model year. Air conditioning was offered for the first time with the dealer-installed aftermarket A.R.A. system. This was the last year a red interior was offered (sold with the white colored exterior), and was the last year for the 1.1-liter drive train in the GT. (Chassis Number starts with #94-1888188)
- Rubber rimmed steering wheel (now often deteriorated)
- Date Code and Chassis Number on left door (latch area)
- Round dash indicator light lenses on dash faceplate
- Evaporative canister in belly pan (next to battery)
- Plastic tray located below parking brake handle
- Turn signal ring in steering column is hinged (high beam switch)
- Cigarette lighter size increased
- Light lens in dash panel above the 6 toggle switches
- Ignition lock cylinder and key changed to BB code
- Vehicle ID strip on top driver's side of dashboard
- Rear axle internal design changed (after chassis #94-2264500)
- Manual Transmission changes (synchros, speedo gear location)
1971 Opel GT:
Major functional changes for the 1971 model year, with relate modifications related to the US introduction of the Opel "1900 series" (Manta, Ascona, 1900) models. The engine was detuned, with hydraulic lifters in the head and lower compression pistons in the block. All speedometers had the "W=1062" calibration regardless of the type of transmission (both 4 speed and automatic). GM introduced its own air conditioning system this year, but according to an owners survey (May 1995 OMC Blitz) it performed poorly. GT sales slowed in 1971, in part due to the drop in power and also the competition from Datsun's newly introduced "240Z" model car.
(Chassis Number starts with #77-2265862)
Quick Look Clues:
- Opening side quarter "popout" hinged windows
- Vehicle Identification Number starts with "77."
- "Opel GT" insignia moves from fenders to rear of car.
- Cylinder head has 4 bearings and hydraulic lifters
- Stock wheel rims changed to "15 hole" design
- Instrument panel faceplate held with 7 screws
- 35-amp alternator option with rear window defroster
- Parking brake indicator (red light) on dash faceplate
- Intake manifold has taller carburetor mounting studs
- Shoulder belt mounts on vehicle posts near doors
1972 Opel GT:
Only subtle differences marked the 1972 model year, most of which debuted on GT's produced after January 1st 1972. Most visible is the dash panel: Radio dial is now labeled "Opel GT radio" (no longer "Kadett radio"), and some of the toggle switch buttons and headlight lever control are labeled with descriptive words of their function: park light, wipe, hazard lights, etc. An annoying seat belt buzzer system was also introduced, and in most cases, quickly disconnected. The 1972 have been noted for having a steady road feel, perhaps due to a redesign of the lower control arm inner bushing sleeves in the front suspension. Also many rear axle housings in early 1972's had the rear sway bar mounts already on them (they were sourced from parts bins of the Kadett line, which was being phased out). Sales were up over the 1971 models, but were not as strong as the 1969-1970 introductory years. (Chassis Number starts with #77-2560567).
Quick Look Clues:
- Writing on interior buttons, heater & headlight panel
- Clock manufacturer changed to Borg
- Engine dipstick goes into hole in block (not tube into oil pan)
- Starter manufacturer changed to Delco from Bosch
- Stock alternator upgraded to 35 amps
- Air filter canister top lid narrowed and internal grille deleted
- Engine oil pan changed to center-drain steel oil pan
- 3-point seat belt configuration introduced
- Ignition lock cylinder and key changed to "CC" code
- Lower control arm inner sleeve widened
- Heater in-dash side ducts connected with rubber vent hoses
- Door glass mounted with round plastic plugs
- Rear axle with rear sway bar mounts (early '72)
- Rear brake shoes & cable with stirrup/hook ends (late '72)
- Thermostat housing changed to 2-bolt design (late '72)
1973 Opel GT:
Significant body changes in 1973, for the last year of the GT's production. US safety regulations resulted in crash-protection bars inside the doors and on the engine cross member. Emissions laws resulted in an EGR valve system. Major cylinder head and timing chain cover redesign, which unfortunately weakened its heat resistance and caused internal cylinder head warpage and cracking. The GT tan interior was brought back, in a lighter "cream" shade. Exterior has the same rims and "split," type round taillight lenses as the Manta, starting midyear on models made in January 1973 up through August 1973. (Chassis Number starts with "OY 0NC2944586").
Quick Look Clues:
- Vehicle Identification Number starts with "OY 0"
- Cylinder Head has 2 allen head bolts to timing cover
- Rear lenses same as Opel Manta's design (after 1/1/1973)
- EGR valve system from exhaust to intake manifold
- Intake manifold has vacuum fitting relocated to engine side below carb
- Carburetor has electric choke
- Engine cross-member protecting plates in front of motor mounts
- Gas tank has extra vent hose to 3-hose fuel filter
- Clutch arm has plastic plug to hold return spring
- Seat belt connects to stiff plastic buckle
- Door pull handle has plastic (not metal) bezel
1974 Opel GT
Never produced. US crash protection "5 MPH" standards mandated installation of large side-to-side rubber bumpers, which detracted from the overall look of the GT in prototype design model. A few 1973 GT's were sold and registered as 1974 GT's, causing a few instances of confusion of actual model year.
The last year of German-made Opels imported into the US was 1975, although Buick used the "Opel" name on imported Japanese Isuzu I-Mark's (which was powered by an incompatible 1.8 liter motor and drivetrain) through the 1980 model year.