First of all, welcome! I don't think too many people on here will be able to help. The B3 and B4 Passats have transverse mounted engines, and the earlier models have longitudinal engines. I would think any early VW longitudinal transmission would work. I found a list from a google search for you.
As far as the clutch, flywheel, shift linkage and clutch linkage go, I do not know. I do know that all 4cyl VWs until MK5s all have the same bell housing. With the right flywheel and clutch set up you could use a 1.6l motor with a 6 speed 1.8t transmission. It will just take some trial and error for you.