I had to move the cross member, and issues with the drive shaft....I don't want to get into it...

All I can say is I like what Sexton said, but I would just match it up best ya can...

Mine was a 30 Spline, it mated to a ZZ4 350 GMPP crate engine, the Tranny was from TCI...>>> I WOULD NEVER BUY A TRANNY FROM THEM AGAIN
But don't let that stop you from using a 700R4 tranny,... I have one that is working in my truck, but I don't know that I will ever feel confident going on a long trip...

While I had my issues with the TCI tranny, I had a local transmission shop rebuild a core, not once, but, Twice, on two separate occassions I had to have a replacement tranny, so I went with a Used and Abused rebuilt core $1500 installed....with this TH350, it rocked, seemed to be a better tranny over the brand new one I had break down 2 times now...

The TH350 is a great tranny, just that folks want the OD, or 4th Gear (.70 over) trying to get a little fuel economy.... and that the 700R4 has a really low First Gear, almost too low...

If you have to have the drive shaft shortened, or lengthend, or a longer yolk going into the tranny etc...

Hope things work out for you...
Good luck.