Previous owner DID say they changed the engine. My guess is they harmed the harness and simply wired in a replacement they could find instead of the proper one. ...Kinda wish they went the extra mile and swapped in a 318... y'know... since they had it out and all. Then again, if they had, they might not have sold the truck.

Edit: Sigh. Drove it to work about 75mph or so, 4 pending codes. P0300, 1, 3, 5. So not my solution... Truck still runs good though, just a thorn in my side. I really don't want to take apart the engine, especially with how it runs.