I guess I should have elaborated more.
And since you brought it up, the heater in the truck was from a '51 GMC (says GMC on the face plate and the heater build plate says: HC-06-51). So I would say that it was originally positive ground. But when put into my truck it did spin in the right direction ..which it is back to spinning now thanks to the instructs of half-turning the shells.
Sorry, didn't think it important to mention it's heritage at the onset.
