help with trans/driveshaft

[dragn91]

I have a 66 gmc it's factory leaf spring inline 6 cylinder 3 on the tree. When I Got it was inline with a 350 auto. Then I put in a sbc in the same spot with homemade mounts. It threw a driveshaft I parked it sold it and just bought it back 7 years later. I'm trying to figure out where the engine mounts need to be and what driveshaft I need. It always had a single peice driveshaft since I had it and I've never seen another one like that but today at the junkyard I saw a 60-63 with a 3 on the tree and a 2 link style suspention with a one peice driveshaft looked very much factory. I think I'm going to go back and get the driveshaft. they want way to much for the trans but I'd like to run it in my truck I like the single shaft but I was wondering if the 60-63 stuff will work with the 60-66 same drivedhaft/trans length ect.. there both long beds as far as I can tell. And is there a difference between those transmissions and the squarebody 3 speed trans?