I have a 73 with the 390 in it. Im not getting fuel to the carb so I replaced the fuel filter its clear and not its not filling up. I need to know whether to replace the fuel pump and or the fuel sending unit in the gas tank.

 

C4AZ-9365-B .. Corrogated Paper Fuel Filter Cartridge (Motorcraft FG-1A) / Available from Ford and autoparts stores.

Applications: Myriad 1964/76 FoMoCo vehicles.

This original fuel filter is located inside a metal cannister that threads onto the fuel pump. Some people are unaware, so they install an inline fuel filter.

If you installed an inline filter between the fuel pump and the carb, the original is so clogged up, fuel cannot pass thru it.
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1971/79 FoMoCo vehicles: At the end of the fuel tank sending units pickup tube, is this little charmer: D1AZ-9A011-A .. Plastic Meshed Filter Screen-3/8" I.D. / Available from Ford and autoparts stores.

Over time, this screen gets clogged up with rust and scale. Be aware that there's another, it's 5/16" I.D. (D1FZ-9A011-A): Pinto/Bobcat/Maverick/Comet only!

 

If the truck had been sitting a while, the tank probably has rusted on the inside. If so the rust could have gotten clogged in the fuel lines.

 

Here is the fuel pump Bill is talking about. After 39 years though there's a good chance that it has the non filter type bolted to it, they're interchangeable.
My guess, if the filters are clear the fuel pump is bad but, before you replace it, there are some other things you can check to be sure.
The fuel tank sending unit, where the fuel line connects to the tank, has a nylon sock filter on it. If your tank has a lot of rust and scale this could be clogged.
Check the fuel line along the frame rail. There are three places that have rubber hose, where the line hooks to the fuel tank, midway along the frame rail and where the line connects to the pump. Check and see if these are hard and cracked. This could allow the pump to suck air and lose it's prime. Might not be a bad idea to replace them anyway.

 

yeah . good thing to work your way from the carb to the tank checking for fuel
had a loss of fuel issue on my '79 F250
filter was clear , hose to pump from the frame rail was collapsed
ran good for 8 months then had loss of fuel issues again
had dual tanks but po on had the rear in place
here the fuel tank transfer switch must've got jarred around was sucking air
short piece of tube to by-pass it and all was good again

make sure you have enough fuel in the tank
get a catch can , take your time , be safe and work your way back to the tank
(then you can curse me out when you have a full tank and need to drop it) :P