Fuel Problem

[81' sierra classic]

This is my problem, I let my 81 GMC 1500 run out of gas. I went and put 5 gallons in it and no gas was going to the carb. So I Went and checked my in-line fuel filter and the carb filter and replaced both. while I was changing my inline i noticed that no gas was coming from the tank threw the line so I blew in the line to unblock any thing in the line, It worked....For awhile about 2 days later it got clogged agian, nothing coming out of the tank. My question is what is clogging in the tank or in the route to the fuel filter.

P.S. I belive that the Electric Fuel Pump is not the problem..

[3 on the tree]

Probably the little filter sock on the end of the pick up in the tank. Running out of gas stirred up all the crap in the bottom of the tank and it got sucked into the sock. try a little air pressure into the fuel line to the tank tosee if you can blow it clear-not too much pressure or you will blow the sock right off. If that don't work, time to drop the tank and replace the sock.