Thanks for the comments, guys! I'm still making progress on this... I really need to find someone to take my 7M engine (or scrap it) so that I can measure out/model up the engine compartment. That will help me out.
As far as the CAD stuff goes, at this point, it's really just a way for me to organize my thoughts/ideas. Once I get the 7M out and the engine compartment modeled, I'll be able to design some engine mounts and get them cut on the jet.
I also need to do some measuring on the trans tunnel and see what kind of work it's going to take to make the 4L80e fit in there. That's another area that I'm still up in the air on! I really like having a manual gearbox in a sporty car... however, I'm not really a fan of the T56. Keeping the R154 (which is in good shape) would certainly be the easiest route, and one that I may persue to get the engine in and running. If it blows, then I can work in the 4L80e. We'll see what I decide on... LOL
Per the transmission decision, a turbo decision will be made. Manual gearbox = GT35s ; else = 62mm or 67mm.
It's going to be a tight fit, but I'm confident that we can make it work, and keep it clean: