Stu Cool
The main external diffenrence between those trannies are the length! TH200-4R doesn't have the replaceble tail like other trannies so it is about an 1" shorther than TH 350 with short tail.
I replace the powerglide with the TH200-4R on my 63 Impala few years ago and It works great! All I had to modify was the transmission brace!
The TH200-4R that I had came originally on Olds Custom Cruiser (307 Olds sb V8) and It has all bolt circels (Chevy and BOP).

TH 700-R4 came firs time in 1982 and it has the same Lockup converter as the TH200-4R untill the mid '80s.
TH 700-R4 Is longer than TH350 with the short tail.
If it's the same length as the TH350 with the long tail, I don't know???

If you're going to install TH700-R4 I suggest '88 or newer from the Diesel Chevy Van and build it to match your engine and differential ratio!

('')
Jani