fuel system trouble

[staggerd86c-10]

this was a challenging weekend, I finally got the a/c working again(partially, ill get to that in a min.) but the truck was mis-firing and i didnt know where the hell it was coming from so i started by changing out the spark plugs then checking the cap and rotor ended up buying an msd hei distributor. all said and done still there. It seemed like maybe it wasnt getting enough fuel but my holley mech. pump is rated way before what i need, so im not sure what i need to do. i changed the fuel line going to the carb and put one that i can put a guage to make sure its getting pressure. i took it out for a ride and the truck ran out of gas again. i thought maybe its the valve that switches the tanks so i bypassed that was running good but once i got on it the truck falls on its face again. I'm not sure what it is thats making it do this but i have narrowed it down that its in between the gas and the pump because the pump to the motor i ended up putting everything new. please let me know what you think. please.