You should be just fine in that power and rpm range, especially N/A. The factory cast cranks are tougher than some give credit for. The Scat seem pretty decent as well. I am planning on tickling 8,000+ with my factory junk. I know others have pushed them a good bit higher before. RPM, balance, bearing clearance, journal diameter, rod/piston weight, compression, material composition, power adder, etc. all have an affect on it.