Hmm, maybe it is the depth then. Although, I would think that would mean an alternator pulley or power steering pulley would be different post-70 as well. If anyone has a 70+ 3-groove pulley and would be willing to measure the depths from the balancer to each notch, I would be interested to do the same on my 69 pulley and post the results. It would be great if opening up the one bolt hole was the only difference.
