I've personally decoded a block from an '84 Crown Victoria that had "XXX" in the lifter valley. Roller blocks didn't come out until '85, and only in the Mustang and Capri in that year. Crown Vics didn't get roller blocks until at least a year after that.
A forum community dedicated to Ford Mustang owners and enthusiasts. Come join the discussion about performance, builds, modifications, reviews, engine swaps, classifieds, troubleshooting, maintenance, and more!