broken 4 speed

[fastlane666]

well i'm new to lateral-g, but i've had my 66 chevelle for 24 years and it's my first car. heres my conundrum; i'm running a built up 408 sbc. about 500 hp.i run a super t-10 lakewood scater shield, center force 11 inch dual friction and a 4 inch high speed balanced drive shaft and 355 gears in a 12 bolt posi. my problem is the trans shifts difficultly at high rpm and i've broken the trans housing on every tranny i've ever used. either through the center of main case or the mounting ears.the bellhousing is aligned within .05 thousanths. any thoughs on why i'm a. breaking housings and b. why can't i powershift this thing?