Hey Hans,
I didn't install my 454 but from the looks of it, they took the mounts and perches, as I call them, from the donor truck and welded them to the 63's frame. As far as the trans goes, I have a TH350 behind mine but I think a small block flywheel will bolt up, but don't quote me on that. Call a Chevy garage and ask some of the older guys there, they have done about everything imaginable to the big and small blocks.
I don't have much hair left but it's not from my truck. It should be a relatively easy swap with some minor engineering to make work.
Good luck and keep us posted as to your progress. Got any pictures?
Scott