Fuel delivery issue

Alright guys this is my first post so I guess I will tell you a little bit about the truck before I go on asking questions.

Well the truck is my mother's it's an 89 b2200 she bought back in 03 or so from a guy down the street. He installed lowering blocks some old school eagle alloys and dual exhaust. Anyways she drove it daily for a few years until she bought something else then only used it on occasion. Well fast forward to 2011 she has her waterpump go out on her about 20 miles from home. She turned it off let it cool down removed the thermostat and limped it back home stopping when it got warm. Once she got back in town she parked it at a family members and forgot about it until last year. She started off by having me replace the water pump as well as the timing belt and battery hoping it would be ready to go but sitting that long I kinda figured it would have a few other things wrong with it. After installing those few things and it not running she just pushed it back under the table. Now I'm trying to get it all worked out before mothers day this year so I got back at it. Over the years the gas turned to jelly and rusted the inside of the tank. So that's where I started I pulled the tank and cleaned it all out as well as the hard lines and replaced the rubber ones. I cleaned the sending unit up real good and reassembled everything and still no fuel to the filter. My next thought was the fuel pump since I didn't feel any pressure on the lines so I went ahead and replaced that with an advanced auto mechanical pump. Still no fuel to the filter so I loaded up the filter with a bit of fuel hoping it would sucke it through but no go on that either. Now the kicker I took the filter off and poured a bit into the in line next to the pump and it actually pushed the fuel back out of the line. I really don't understand what would cause this as I installed it the way I took it off and the return line and in line are different sizes so the lines are correct.

If anyone has an idea why my pump isn't pulling fuel it would be a great help. Thanks in advance.

Sorry this post is pretty messy but I'm on my phone and it's hard to edit with such a small window.

What about the fuel sock on the fuel inlet inside the fuel tank, could be plugged. On a 5-speed there is a fuel filter in the engine compartment not far from the fuel pump.

I cleaned the the sock and replaced the filter. All the lines are clean enough for fluid to pass. I suspect the pump since it won't pull fuel from the filter but it's a brand new pump.

Pull the line from the top of the carb and see if fuel starts pumping. If so, there is a filter inside of the carb that could be clogged. It is held in place by the 13mm bolt and metal pipe that the rubber line plugs into. Maybe the float is stuck. That would be something else to check.

Alright thanks will do

"All the lines are clean enough for fluid to pass. I suspect the pump since it won't pull fuel from the filter but it's a brand new pump"

I suspect that the feed line from the tank to the mechanical fuel pump is full of air; fuel pumps are designed to pump liquids, not air. Once can try to prime the engine to start using aerosol starting fluid, that might get the fuel pump going fast enough to get the air out of that line and fuel through. But I think you may need to pull the fuel line off the fuel line inlet and use a squeeze bulb, hand vacuum pump, or similar to pull the fuel through (be careful of explosive, flammable gasoline), and once the fuel starts coming through, attach the line to the fuel pump inlet. Maybe jack up the rear of the truck to get gravity to help.