Just some friendly advice.
I swapped my 700r4 transmission for a TH350. When installing the transmission I ran into 2 mounting issues:
1. The mounting bracket would not line up with the hole in the crossmember
2. The bolts I was using to hook up the TC to the flexplate were HARD to turn
To fix the mounting problem, since the placement of the trans mount was different, I made a 6"x6" metal plate (1/4" thick) and drilled 4 holes in it. 2 holes for where it would mount on the bottom of the tranny and 2 holes for where it would mount on the actual mount itself, thus making this an offset mount. To mount it, I used the same bolts that came out of the 700r4 trans mount and just bought 2 new ones along with some locking washers and nuts. I installed the old bolts to mount the plate on the transmission and the new ones with the washers and nuts to mount the trans mount on the other end of the plate. After that, everything else mouted normal.
To fix the HARD to turn bolts, use standard thread rather than the metric thread. Make sure the bolts are short as well because the bolts that came out of the 700r4 were too long, thus causing a loud rattling at cold startup that would quiet down after about 1.5 minutes of idle. Come to find out, the bolts were tightening up but were not securing the TC to the flexplate causing the loud rattle. Just make sure you get some short bolts and you'll do fine.
HOPE THIS HELPS ANYONE SWAPPING TRANSMISSIONS!!!