The TCI street fighter transmissions are only rated to handle 450hp applications.
You may want to check into it and do a little research. I'd email TCI tech for help.
Have you thought about just buying a trusty TF-727 and getting a pro shop or trans shop to beef it up?
A stock TorqueFlite is as tough as nails so you don't need to do much if anything just performance mods.
New valve body, bands, converter......
Good luck and let us know what you end up doing.