I too have small bits of nylon cam gear, or hardened valve stem seal sneak thru that stupid hole that Ford put in the oil pump pickup screen on many of their engines. However, in my case, when the oil pump locked up, the distributor roll pin didn`t fail, rather, the oil pump hex shaft twisted up like a wrought iron bar, and snapped the end off. The only time that I ever experienced a sheared distributor roll pin, was on Mallory YL style distributors. For whatever reason, Mallory used a roll pin smaller than OE Ford, plus the gear was not much of a press fit either. Had the Mallory roll pin fail on both my 66 Fairlanes 390, and the 428 CJ in my 70 R code Mach 1. Neither engine had anything in the oil pump, and a new roll pin got the cars running again, although I replaced both Mallory distributors with Accel Dual Points, and never had any more issues. Never had a Ford distributor break a roll pin.