This is a solid post A 4340 forged crank with a 4" arm has around a 7300 rpm max safe limit providing good balance, A factory block, depending on sonic numbers and expertise in machine work and assembly have a variable that's hard to nail down <Most seem to think 600hp is getin close to the top> I see dyno sheets of 650+hp @ 7500 rpm on lots of factory blocks? Either way 7500 is exceeding the safe crank rpm in most stroker cranks, is trying to stay under the safe rpm just leaving too much on the table? Is the duration of High RPM short enough to bump up the RPMs, When they quote a safe FPM is that for continuous or intermittent use?