Hey guys, I'm looking for a little knowledge that I haven't been able to pin down. I'm pretty new to Fords, but have done tons of research and have a pretty decent idea of parts and such. On to my question.... I've got a set of GT40 heads. They are cast F1ZE-AA, so off of an Explorer, I presume. My question is about the date and letters that are on the front of both heads right under the freeze plugs on the milled part of the head. They both have "10/94" and the letters "PBF" on them. I'm not asking because I think I have something special or anything, but curiosity is getting the best of me! Haha. Thanks a lot, guys!