1989 Nissan D21 fuel system problem.

Ok. I got a 1998 Nissan D21 4x4 extended cab 3.0L free, it needed Frame and body work. I had to replace the gas tank. Once I got it all back together and tried to start it, it just cranks. It does not seam to be getting fuel to the carb. I hear the electronic fuel pump run but again no gas to the carb. Any ideas or do I need a need fuel pump/sending unit. BTW the fuel filter is new, also the tank is now full, but the gage in the cab shows empty. So any sugestions would be great.