Well, its not too hard to check if there is a ground problem. When the alternator is running, measure voltage difference between the Battery Negative and the Regulator body. Then check the mounting bolt and the body if there's a measureable difference.

While at it, measure the voltage difference between the blue wire and the regulator body. This is the voltage difference which determines how much current the regulator will let through the field. Lets say it is low due to poor grounds or poor connection on the feed. Either way, it might result in the regulator trying to max the field and eventually overheat itself. Just a possibility.