I found the answer to my question...
Looks like they were rear wheel drive, but used some sort of auxiliary gearbox behind the transmission to drop the driveshaft down super low to allow for the floor to be very low.
In swapping in a new engine and transmission, it sounds like you'll either have to engineer a way to get the driveshaft lowered down like the original design did, or build a tunnel down the middle of the floor, which would be a real challenge to design the interior around.
Also, it sounds like the original drive axle is designed for an input rotation that's backwards from modern drivetrains. So like cowlitzcoach suggested, swapping out the drive axle might be a really good idea.
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He's a member here also. If you can get ahold of him, he could probably provide you with some pretty good insight. His user name is karlw. Here's a thread he started sometime last year... http://www.skoolie.net/forums/f11/19...html#post80235