It doesn't take much to hold that power level. Good front drum ( I like aluminum), a steel front planet, deep 46RH trans pan and filter extension. Good solid KD band, good quality frictions, and a Ultra sprag. Coupled with a good trans brake valve body. A&A is a good source for the parts. The assembly itself is pretty simple. Pro Trans stuff is the fiest. But it's not priced for the faint of heart. This combo I've listed has served well both in my 580" 64 Belvedere and my sons turbo SB 62 Savoy. Both make over 850hp.
Doug