My 1983 Cutlass was a V6. It`s now a 430 Cu In Buick, 1967. I plugged the return fuel line at the tank and on the fuel pump. Now the fuel pump has quit working and I`m considering going to an electric pump. I`ve only driven the car 50 miles and it seems ok with the return line blocked but wonder if that led to the pump failure. Also not sure what kind of gas cap to use: vented, non vented, pressure, etc? Any input appreciated.