Yeah that's tough about the mount points... The only way that I could see doing it would be to have a tube chassis tied into the frame horns at the transaxle. Then the trans would have to be solid mounted to the frame. Oh yeah, don't forget the rear engine mount. LOL But seriously, if someone found an old double cab that was too far gone to do a correct restoration, it would be kinda cool to put that kind of body on a frame with some real horsepower. It sure would be one conversation piece. I grew up around old VW's, my grandfather had a '67 21 window microbus, my first car was (still have it) a '67 bug. I also have a '61 bug and a couple of years ago I traded my sister a '56 oval window bug for a boat. I sold the boat and she still has the bug.
I may like to go fast in my bug, but all of the modifications that I have done could be undone with some wrenching to return the car back to stock as I don't really believe in cutting up old cars.