Rip-It-Up, as far as the cross member... I think the TH400, and any of the manual Tranny Crossmembers are different, even for the short shaft TH400 (but don't quote me) And the yoke on the TH400 are usually larger than the rest... so you'll have to double check that.
For the bolts and perhaps the crossmember besides ebay or some place you might try: http://www.gmsportssalvage.com/ for good used stuf all GM. Or for new stuff: http://www.theengineshop.com/ They should have what you need. Or for pure modification sites and information: http://www.racehome.com/index.html or http://www.pro-touring.com/ But they are all around High Performance, and into major suspension stuff, more than straight line stuff. But at the same time, they do lots of cross platform swaps and would likely have all the answers to your questions for sure!
So let us know how it works out, and get some pictures up!