If it’s been sitting a long time, I would about guarantee that it has valves stuck open. Very common on old flathead Mopars that are left to sit. Easiest way to fix that is to pull the head, spin the engine over, tap stuck valves down gently with a rubber hammer. A little Marvel down the valve stems seems to help really get them working good.
And it will be a 6v positive ground system. Mopar changed to 12v Neg Ground in 1956.
