Losing Gas - 1988 B2200 Long Bed Carb
 

I had an issue today where the + battery cable was lose.
I put $20 worth of gas in the tank.
Got a jump to start the truck and drove to the parts store to get a new + terminal. I turned the engine off and later I had to jump it again. The guy helping me connected the battery cables backwards and we got a spark.
Once the truck started again I noticed that the gas meter showed almost empty. I put $6 more of gas in and thought the fuel sender was lying to me. I ran a local errand, within a mile of my house, and ran out of gas before I got home. When I ding the side of the gas tank it sounds empty. There is gas in the fuel filter. There is no sign of a gas leak but seems that I am losing gas between the gas tank and the engine.
Any suggestions or a point in the right direction would be much appreciated.

Bill