Basic Magnum question: Safe maximum RPM on stock internals?

What cam do the 300HPs have? Power backs off after the peak, on stock motors it starts dropping at the latest around 4500. There's a lot of minor factors like having more air intake or better exhaust that will extend it a little or limit it more if there's a restriction but the stock Mags lay over before 5K. How high it can turn- I really can't help but think so much of that has to do with maintenance. A good motor that's always been well-kept, seeing up to 6500 doesn't hurt many cast crank short blocks but that doesn't describe every motor you see and sometimes the better kept can be significantly higher miles and still be less likely to fail.