Here's a post-'69 350 from a Caprice, and again the stock timing tab (ARROW) works great but a swap to a short water pump necessitates using that aftermarket tab, and here's the problem. The timing groove is way off. The solution? Set number one to TDC using the original tab, then mark another line on the balancer to correspond with zero degrees on the new tab, and you'll have no problems setting the timing. It seems obvious but is a common mistake.