383 is original '71 bottom end.just a bigger cam/head work. was a race car since the late 70's. has a high stall convertor that I want to change anyhow. just would like to know if the 400/440 ext balance harmonic balancer that I have will work? or do I have to use the correct pt# balancer that the 72' 383 calls for? I don't want to hunt that one down just to find out the only difference is the pt #.