I just swapped tanks in my 78. The old one looked as if the PO took a sledge hammer to it. Before I swapped tanks the 31 gal. that was in it would only allow me to put approx. 5 gal. in it before the pump would shut off and the gas guage always showed 1/4 a tank. I assumed because of the massive dent it would only hold that and after about 5 gal. of gas my blaze would stop running. But when I pulled the tank it was full and had 20+ gal. in it. The new tank is in and everything works but my guage. I put about 5 gal. in it at first and the guage shot straight to the right and even after filling it it stays there. I bought the tank and sending unit on another board and its a 25 gal. are the guages different between a 25 and a 31 gal. tank?