Ive done a bit of reserach on the 500 caddy swap myself and these guys are recomended by people on other boards.
Try
www.500cid.com The projects section is great. Have a look at Crazy Joes VW!
From my research the best year is a 71 Eldarodo as it has the right sump. Remote oil filters etc are available. Just do lots of reading as the answers are out there. One of the guys here has done it, I think it might be 2-Ton but may be wrong.
Use the search on this place too for "500 caddy" as there has been some discussion in the lounge about this previously. Good luck.
