I've been thinking about this because I've been toying with the idea of putting a Type 4 engine in my 67 bus. I've got a book on converting the cooling system to the upright Type 1 system so I can mainatain a 'stock' appearence.
Its my understanding that the flywheel size is the same for all buses from the first 12 volts in 67 up to the vanagons. Of course there different flywheels for different engines but the overall diameter is the same since 67. The old 6 Volt buses and bugs had smaller diameter flywheels.
There is different clutch disc sizes from 180MM (6 volt bug) up to 228MM in the late bus (74 and up) and vanagon. Type one powered buses, from about 63 up to 71, used 200MM clutch discs while the bug didn't go that size until 67. Up to then they were 180MM.
VW changed the type of throw out bearing in 71 from a 'floating' bearing to one that rides on a sleave. The way to tell is the pressure plate. The early ones have a washer where the throw out bearing meets the pressure plate. The later ones just have 'fingers'.
In the old days, people would grind out the bell housing of a 6 volt beetle to accept the 12 volt flywheel. If it was a 6 to 12 volt conversion, many would just leave the 6 volt starter and flywheel. The started turned faster, but would take the extra power in short bursts. Most of the time the engine was turning fast enough that it would fire almost immediately. I didn't have any trouble with my 66 bus that someone convertered to 12 volt and left the 6 volt starter and flywheel.
The one question I have it why did you want to put the larger clutch in your bus?
