I know a 1972 520 stroker with .600 final lift and running a tuned up six pack setup produces 600 horses...he has broken his tranny and his hime joint on his torque strap....8) and that is with 440 Sources stroker kit
Hate to quote myself but contact Andyf and he might agree that a stroked 400 block might be better because they did some changes to the mains and webbing....JAT