Question: What size engine can I put in my Bug or Bus?
Answer: I think that the normal 1600 cc, late model dual port, dual oil relief engine will fit in nearly all Bugs and Buses. I'm not positive, so if you have doubts, or if you have an especially old or new vehicle, you should check and engine interchange book.
Fitting a type IV engine is quite a bit more work. I think the transmission connection is similar (or identical) but exhaust and engine cooling are quite different. Besides, the type IV engine is special, and special means expensive.
You can go to 1641 cc by only changing piston and cylinders. 1776 cc needs minor engine mods, but I think this is pretty easy. Larger displacements get more complex, and make a LOT of heat. Heat kills VW engines, so if you want reliable, kee the engine size smaller.
More car and motorcycle sites at laudeman.com
Links to some of my other sites and friend's sites:
Proficient Motorcycling : The Ultimate Guide to Riding Well
Read my review. Get the book.