The 250 or 292 pump. I have machined an adapter that allows it to be mounted to the bracket for the OEM pump and driven by the distributor, but that procedure isn't for someone who thinks OEM is the be-all and end-all in every application. I'm more concerned with results than being obsessed with correct part numbers. The 250 pump also costs less than half the price of a numbers-correct pump. I've also adapted a small block Chevy water pump to an early Chrysler hemi engine, the one that's virtually nonexistent for the original application.
The Melling M-45 we put on John's 261 ran 40+ PSI at warm idle, and much more at highway speed.
Jerry
