"safe RPM "

Last 440-452 that i ran with the block partially filled with casting epoxy and "cap straps" that i make main studs with ported max wedge heads dual dominators on zeeker tr 750 roller, made about 775hp. motor would go to 7500 no problem but fell off after 6800-7000 even with all that hardware.never hurt the block but it crack stock steel cranks. that being said i would say 6500 max if everything is done well but i would try to make power lower and try to keep it closer to 6000 and let the torgue work for you.with those heads ported on that big a motor it will flatten by 6500 or less anyway.paul