904 or Powerglide???

thanks mate ,yes we love the 4 doors over here, we like our family race cars
what tips for the 904 mate ,just rebuilt the 9 inch diff with a strange carrier,yoak ,full spool ,3 1/2 inch tail shaft etc the 904 is stranded with fmvb and low gear set ,what other mods does she need , trying to run a nine @ 135 in a heavy car 700 hp dont wont to brake trans. ian