When you say well grounded, the actual regulator is bolted to the fender, but am I correct in guessing that the green wire that is attached to the top of the regulater is the ground?
Green wire is the field wire. Everything on the car is chassis grounded by the screws and crap that holds it together.
Some will take the part from the box and plug it in to try it before ever bolting it down. That can kill the new part.
Good luck