So I have a "junk yard" motor and its not original. Great! So I really have no clue how many miles are on this thing then.
As Wade said, it's just the head. I mentioned cylinder head and/or engine since a salvage yard worker could've stuck that tab on the head when it should've gone on the block, or both. Giving them the benefit of the doubt, that head (at least that one) has been replaced. But, the whole thing could've been replaced and those heads could be original to that block. You'll never find out unless its documented somewhere or if you can contact the previous owner(s). If you're lucky, it was documented at a dealer and, therefore, should be traceable with an AutoCheck or maybe CarFax report. Grab a flashlight and look for more of them tabs. Yards usually stick the tabs on the rear of the engine block, just under the head but above the bellhousing mounting surface or, more commonly, on the side on one of the cylinder walls.
Just because an engine comes from a "junk yard" doesn't mean it's junk. To me, a "junk yard" is where generally anything "scrap" is dumped. A salvage yard is just that- to salvage. Meaning there's still good parts to be had and not junked. Also, the yard must've thought highly enough of that part/those parts to warranty them and installed that tab/those tabs to help uphold that warranty.
You know how many miles are on the vehicle, not necessarily all of its parts. Mileage isn't exclusive to the engine. I'd venture to say that that engine is in better shape than what was in the truck before it.
