Upon closer inspection, the distributor gear showed circumferential wear with chips starting at the bottom of the gear and distortion of the pitch. This probably began with initial startup until the weakest gears failed. I don't think that it was related to a seized pump because the roll pin did not shear and the pump still turns through 360 deg. Until the post by dscott I thought that there may be a different ford gear for the a351 cam but maybe not. When I pull the motor I will remove the cam and burnish the gear if it appears undamaged. Thanks to everyone for their assistance and kind words. It's nice to know that one is not alone in this universe.
