That Airstream is no lightweight.....I am very surprised he was able to keep the little 700R alive and kicking.....

Yeah.
The good old days... when life was a simple bolt in option to make just about anything fit anything else....

Yes
The small bolt pattern flex plate and the large pattern.....The 6.2 with the 700R (Or TH350) got those and the 6.2/6.5 with the TH400 OR 4L80 had the large 6 bolt plate.....

If you go to the DB2 Pump and a hydraulically controlled 700R/4L60 Then the electronics really means ZIP......It will all work fine.....

Trying to get everything to run with the DS4 becomes an issue when you start swapping goodies.

Not impossible...but annoying at times....