I recently purchased a 454. I know the motors are externally balanced from the factory. I have seen flywheels/flexplates and harmonic balancers offered in both internal and external balance. The motor I bought was originally in front of a 4 speed manual, and I am bolting it in front of a 4 speed auto. I removed the flywheel and behind it was a "balance plate" of some sort. If I order a flexplate for an external balance motor, do I need to reuse this counterbalance or was that just for the flywheel? Also, the harmonic balancer on the motor looks like the one I have on my internally balanced 350. I "thought" that externally balanced harmonic balancers had a step or counter weight attached to them. Can anyone help, I don't want to ruin this motor. Also, who offers retrofit roller camshafts for BBC's. Thanks.