Balanced 360 Motor w/4-speed?

I'm buying a 360 motor from a friend and he tells me the motor was balanced with his torque converter. (He still has the 904 and converter).

Would I be asking for trouble if I just slap on a Mopar Perf. externally balanced fly wheel for my 4-speed? Should I get things rebalanced?

What should I consider?

Thanks,
Jeff