I dropped off my block at machine shop other day, and asked about balancung the crankshaft, wheter i needed to get all the pistons, rings, etc. For him to weigh them and balance. I had seen it done on utube, so was asking what he needed. He asked me if the balancer was internally balanced or not. He showed me a balancer in his stock, and showed me how the inner part was partially ridged. He saud the other type was fully rounded over the circunference of the balancer, so, my question is which would be on the 63 390 engine.