’58 Lark, right? Yes, they had a single line tank..Your fit probably is ok. See those two little pins that get pushed in when you attach the connector? One is a fuel valve and the other one is a vent valve. The one with a tiny brass washer around it is the fuel valve. There is a micro-sized o-ring behind that brass washer. I’ll just about guarantee that teensy o-ring is shot. That lets it suck air and slop gas out.
The o-ring is replaceable by knocking the core plug out of the backside. There are two sizes of the tiny o-ring. ’58 uses the smallest size. There is another o-ring in there too. Replace both.
