See my other guide for VW sidewinder key applications for the MK4 vehicles.
Volkswagens have nicknames for their models, mk1 mk2 and mk3. These nicknames are just that. There are engineering changes to all models through the years. Asking for a part " I have a mk2 Jetta" means very little. It is like calling the parts store and asking " I need an air filter for my ford" Without a year, it is useless. The Scirocco uses the mk1 key from 1974 to 1979, the mk2 key from 1980 to 1987 and the mk3 key from 1988 to 1990. So using the nickname to ask for a part can be a problem. The Scirocco is a mk1 chassis from 1974 to 1990. The cabriolet is a mk1 chassis from 1980 to 1993 but uses the HV keyway 1980-1987 and the AH keyway from 1988 to 1993.
Starting in 1974 the Rabbit and Scirocco are refered to as mk1 or mark 1 vehicles. The keyway is VB. It is double sided (mirror image cut) with a high groove. In 1980 with the introduction of the Jetta and Cabriolet the keyway was changed to HV with a low groove. The mk1 Rabbit and mk1 Jetta ended in 1984 but the Scirocco and Cabriolet continued production with the HV keyway untill 1987. In 1988 the keyway changed to AH with a step and no groove. Known as mk3 these vehicles are still mk1 cars. From 1993 this keyway continued untill 1999 with the Corrado, Passat, Golf, Jetta and Cabrio known as mk3. Quantum (known as Passat in the rest of the world) started in 1982 replacing the Dasher uses the HV key untill 1987 then changes to AH.
The mk2 keyway HV started in 1980 but is better recognized as appearing in the Golf and Jetta for 1985 to 1987. This HV keyway is the common replacement key (stewy griffith football head) found in most home improvement stores and retail stores. It will fit all 1974 to 1999 water cooled engine Volkswagens. It is the universal replacement key.
The mk3 keyway AH started in 1988 but is better recognized as appearing in the Golf III and Jetta III. All Corrado and Cabrio are AH keyway from 1990 to 1999. Passat 1990 to 1997 are AH.
Valet keys: Valet keys have the same cut as the main key for the car. Their keyway is different. 1988 and newer cars have the AH keyway. Their valet key is the VB, also know as the AN. The high groove prevents its entry into the AH trunk and glove box lock. The AH key will not fit into VB locks.
So if you have a VW, no matter what key you have, no matter what model you have, the correct keyway is VB for 1974-1979, HV from 1980 to 1987, and AH from 1988 to 1999. Engine and transmission have nothing to do with keys. Locks have codes stamped on them, your serial number (vin) has nothing to do with the key.
The Dasher know as the A1 chassis uses the VB key through 1981. The glove box lock keyway is FB.
The air cooled engine cars:
1967 to 1970 type 1, beetle, ghia, and type 3 squareback, notchback and fastback are series K keyway. The Type 2 bus and Thing are the L keyway.
1971 to 1979 type 1, beetle, ghia, and type 3 squareback, notchback and fastback are series M keyway. The type 2 bus and Thing are the R keyway.
1972 to 1974 VW 411, 412 use the VB key. The 1968 to 1970 411 uses the VA key.
1960 to 1966 beetles can have 4 differnt keys, SE, SU, SV, SC. The SU and SV are mirror images of eachother. When these keys retired as door and ignition keys, they continued their use as the glovebox key thru 1979. The SC is the glove box key for the Vanagon. Aftermarket ignition switches from 1960-1967 use the E key.
Do not judge the key applicaton by the shape of the head. Many keys look alike but the keyway is different. 1967 to 1979 all look alike but there are 4 different keyways, 1974 to 1999 have at least 12 different heads with 4 different keyways.
See aircooledkey.com for more information on volkswagen keys. This is just a brief guide.