And so the story goes..hmmmmm sounds like you got one Hot engine- these car crooks nowadays do exactly that....one scratched off number here and there and voila, some guy desperate to buy a new motor on the side, gets one 3 days later of course with missing mileage etc etc.

To solve your problem much as I hesitate to be involved in this shady debacle, I'd just follow what some guy said. If you cant remove and compare, just buy em both. Try fixing the first, if it works, then take the other one back and vice-versa. Thats just a commone sense approach to it They are only 40-60 bucks I think. If he wont return it, sell it on ebay...its still cheaper than paying labor for 1 hour for the install.