You're right tclederman - The '54-'55 sender unit and pick up tube are a combined unit assembly coming out of the top of the tank. The '48-'53 has the pick up tube coming directly out of the front side of the tank just below the seam. If you are using a'48-'53 tank with the '54-'55 sender unit ,you will need to block off the original pick up tube hole, with either a plug or go to a radiator shop and have the tube cut out of the tank and a patch blazed on to cover the hole. This "reconfiguration", that I mentioned in my previous post, I did putting a '54 1 ton panel truck tank into a '48 1 ton pick up. Now as to the 12v /6v, the sender unit doesn't know the difference between 12v and 6v. BUT - the gas gauge will need an inline voltage reducer or you will burn out the 6v gas gauge if you convert to a 12v system.
