All 700R4's & 4L60E's use the same gear-train/internals. As the transmissions evolved they did make refinements to parts.
The input housing for instance changed to allow for thicker steel plates in attempts to reduce heat related clutch distress. They improved torrington bearing sizes for longer longer life, but the basic design remained the same. Reverse input drum feed orifices changed and pistons were made larger for garage shift feel and low mileage clutch distress. As electronics came out a lot changed, but the gear-train stayed the same style. I use a 4L60E input drum in almost all my 700R4 builds. Again refinements to a basic design were made.
Originally the basic difference between a 4.3L V-6 & a 5.7L V-8 700R4 unit fell on the pressure system & 3-4 clutch capacity, 2nd servo size, governor & valve body.
1)The 700R4 for a 4.3L(first year 1985) in the beginning had a .420 boost valve & the 5.7L had a .470 boost valve, along about 87 the 4.3L ended up with the .470 boost valve too.
2) the 3-4 clutch in the 4.3L had 5 frictions & the 5.7L had 6 frictions. this was done by simply replacing a friction with a steel plate
3) the V-6 units got a 554 servo that was larger than the 553 V-8 servo. This change had to do with shift feel and the fact that a V-6 engine produces less torque than the V-8
4) the governor weights were lighter on the V-6 over the V-8, this allowed the V-6 to have slightly later shift points across the ranges.
5) the valve-body had different shift valve sizes and spring rates between them to allow for the differences in shift timing the engineers wanted for overall drive ability.
As the 4L60E was introduced the internal differences became smaller because, hey it was electronically controlled. the shift feel and schedule was all done in the PCM programming. Electrically is a whole other Oprah show.
So the changes between the V-6 & V-8 became the pressure regulator boost valve, the 2nd servo size and an accumulator valve. All of these are for overall shift feel.
So the real bottom line is, don't put a V-6 unit behind a V-8 if you want it to last. You can put a V-8 unit behind a V-6 and other than slightly firmer shifts, you'll probably never know.
Any 700R4 can be built to handle the Torque/HP you require...