322 to 401 swap

can anybody out there tell me what problems I'll be facing if I try to put a '63 Riviera 401 nailhead in my 56 Special? It has a 322 right now, but it is very tired. Will it just drop right in? Will the torque tube work with the newer tranny?? I know one of you out there has done this before, and I would sure appreciate it if you'd let me pick your brain.

Thanks, Mark