fuel tank issues in Oscar the grouch

[WarMonger]

got on the freeway tonight and felt the truck spudder. Then about 1 mile down the road it died. I figured it was the fuel pump. Wrong!! Once i got it back to our shop we started checking things out. pulled lines and was not getting any fuel. I then pulled the line from the bottom of the tank and no fuel came out. The tank has about 3/4 fuel in it. So I took my air line and blew air from the supply line at the bottom of the tank into the tank. You could hear the air go in, but no fuel came out after the i stopped the air. Then we took off the gas cap and shot air inside the tank. Nothing came out the hose, but then fuel started to pout out. What is loose or floating around my tank? Is it that sock filter thing? It is the stock tank behind the seat. Looks like it is very clean. I hooked up all the lines to move the truck around the shop and it started and ran fine, but i'm afraid to go anywhere in it till I figure out the problem. the line at the bottom of the tank was very soft and felt like it was half collapsed, but not sure if that is the problem. What do you guys think?

[Boog]

If this is the original in cab tank i would pull the sending unit/fuel pickup out and have a look at it and with a trouble light look down inside the tank. Who knows what could be in the tank after all these years. Soft rubber gas hoses need to be replaced anyway.