Your max rpm for your big block????

All depends. I do the same mods as the small blocks... higher relief pressure, standard displacement pump, MP drive, enlarge the main feeds, blend the sharp turn in the pickup fed passage, make sure clearances are good and there's minimal taper. Depending on the parts, the build, and the need, that will take it safely to 6500-7K. But above 6500, you really need to pay attention to block machining, main webbing, and bobweights. The stock botton ends are pretty bulletproof to about 6K if the machining is good.