@ Techone,
Yeah, the on board 7805 can handle 12v, however, I get anywhere from 12.2 to 13.5 in my 69 El Camino. Old car, and though a lot of it has been computerized (ignition, air intake control, etc), the alternator puts off varying voltage depending on temp, rpm, how hard the bass is hitting my subs and whatever else may or may not be running off of it. Sounds odd, but I had the same issue with the old alternator setup as well before I switched to the current 300amp model.