[Jeff H]

Sounds interesting. My first thought was if the mechanic took the engine/trans/radiator/hood and disappeared, he might have swapped the rear as well. With all the COPO indicators you say are on the car, it's hard to imagine someone knew all the details to try and build a fake COPO way back then. I would check the rear closely to see if there's any sign it was removed or replaced at some time.