Well actually I have a 454 pushing 550 horse without spray. a turbo 400 trans(not beefed up yet). But i saw a 12 bolt gm open 331 gears, i figured i would change the gears anyways. It has no backing plates but I heard thet the ones from a 10 bolt will fit? I was planning on running 410 gears? What you guys think? Thanks, Brian