I run a 8 1/4 with 3:73 sure grip behind a 470" stroker 4 spd in a 69 Bcuda. I'll guess it north of 525 hp. It's been in there for years...zero issues. I don't put sticky tires on it and I don't do 5k rpm clutch dumps. With 255 BFGs they lose long before the diff does....the tires are the fuse. If they spin the diff will live a long life.