Anyone bother to look at his feedback rating? Only 1 feedback in the files! I would definately tend to believe that this stuff is "off the back of the truck". It's obvious he's a kid, look at the way he writes. Here's my theory:
The stuff MUST be stolen, because no one with enough money to purchase that stuff legally would need to sell it to make more money, it's a waste of time. It's also pretty clear that these aren't "spare parts".
I second checking with the authorities. If anyone is in his area (Riverside, CA according to his eBay profile), please call the local sherrif's department/police station to find out if anyone has reported a large amount of auto parts, specifically engine parts, stolen lately.