Ok fixing this 15 year issue and a 727 question

If you are destroying that many transmissions, "something is wrong." Either the rebuilder is an idiot, or your kickdown is killing them, or "something."

The whole deal with kickdown is that there are many OEM pieces, just like drive pulleys, and "they are a zoo." If you don't have a known good compatible setup, I would just go with a cable of some kind

I don't really know much about the driveability of 380hp crates, but not really sure you'd be happy with a "bone stock" stall converter.