Your max rpm for your big block????

My engine has been together since '88 and I used to turn it to 7200 all the time for years. Then I went to the track and found out it quit making power around 6300 with stock port 516 heads so that's where I shift at now until I get some nice heads. 383 stock stroke, milodon single swinging pickup, roller lifters, cross drilled crank, balanced assy etc.