I have a DIAE-8509 pulley. It's a 71 Full Size, but fits what engines and models of cars? Any help? Thanks

Full-size is a certain group of the models of cars. Such as Galaxie, station wagons, early Torino (pre-69) and likely more. As for the engines - it may have been used on various engines and even on models one or a few years after the fact. For example ford used the exact same washer reservoir motor from a 1969 model and I recently found one in a 1971 reservoir. I matched that to the motor from a 1973 reservoir and they all are identical. If parts left from earlier production runs worked/fit properly- they were used and smaller numbers were sent out as service parts. Sometimes they went to a new part number for the year - and sometimes the old numbers kept coming (cutting the necessity for extra number stamps in production).