is there a difference in 700r4s between v6 cars and v8 cars? internally?

 

yes. they are different parts in the v6 vs v8 cars
and the cases are not interchangable.
There are lots of differences.

 

Less clutches and thicker pressure plates are used. The factory will not build a trans heavy duty if it wll live thru the warrantee with less. No point in spending money to make a 200 hp car have a 350 hp trans. It's all $ and cents to gm. Do not flame the hp numbers. They are hypothetical to show example.