Fixing some leaks

[Mryan]

I bought a 71 GMC 1/2 ton 4x4 in April and have been fixing up the drivetrain from leaking on my garage floor.
It has a 4sp Sm465 Muncie trans and a NP205 transfer case behind a 454 that was installed at some point in its life. I am planning on pulling the trans and transfer case to reseal both. Two questions;
1) Is there a "standard" clutch diameter? I would like to have a clutch ready to change during installation.
2) I have had the trans crossmember out and it is only held in by four bolts on the bottom side of the X. When I tried to line it up with the top holes I could not get any bolts in. I assume this happened during the big block transplant. So while the trans and transfer case is out do I try to get this aligned and top bolts in or drill upper holes and install top bolts?

I use my truck as a driver and a truck, it is not a show piece but a cool old driver.
I would appreciate any advice you can lend.