A stock GM block will handle 725-750 h.p. with good caps, the block rocked to the bottom of the freeze plugs and studs.In the late 80's I use to run a 468 with dimple rods and a factory steel crank and heavy 13. to 1 TRW pistons.Rec. port heads every weekend.I would shift at 6,800.I could get one full season out of everything without having problems.With a light-weight 4340 roatating assembly 7,500 is very possible.Add aluminum rods and it will go 7,800-8,000.But keep in-mind the aluminum rods are used for one racing season and thrown away. Some time compare a BBC with a 460 ford.You soon see why most people prefer the BBC over the 460 for bracket racing.