ok i have a 89 k5 with a 305 i put in and now fuel pump wont work ,checked ground its good i have power to sending unit (gas gauge only) but no power to pump changed cpu ,there is 2 wires to the pump just wondering if both are supposed to be powered

 

Here is a wire diagram of the fuel pump on your truck. And a location of your fuel pump relay.

If you look the orange wire at the relay should have 12v all the time, first check to make sure that is correct.
If not fix the fusable link on that wire from the battery.
If you have 12v there check to see if you have 12v at the tan/wht or pnk/blk wire while the engine is cranking.
If you have power while cranking, your fuel pump is bad of your wire is broken from the relay to the pump.
If you have no power there use a jumper wire and jump 12v to the dk.grn/wht. If this doesnt turn your fuel pump on replace the relay.

Most likely its the relay, power wire, or the pump is bad.
Hope this helps if you need any more diagrams liet me know.