Harmonic balancer

So I have an 88 5.0 nonHO roller motor, and I am planning on using the harmonic balancer from that and installing it on my new 306 roller. The donor motor has over 100,00 miles and there was a noise in the crank near the rear of the block. I have heard a few reasons for this. One person told me that my crank pulley and harmonic balancer was bent and that was the cause for the crank noise in the rear of the motor.This was just one persons oppinion, but when he pointed it out to me it did look 'wobbly', but the car ran smooth and eventually died because of cooling problems. Someone else said that the setup was not bent and that it is sometimes common for some 5.0's to go bad like that with the crank in the rear of the motor.
I have Serpentine belts. Any feedback??? I would like to save cash and use the old but not visually damaged pulley and harmonic. What are the possibilities and issues that I should consider?