92 f-350 460 fuel problems

Please help !My 92 ford needed a motor rebuild so i did now i have fuel problems on the fuel rail there is 20 psi . If i undo the fuel rail and test the fuel pump i have 60-70 psi . I have changed the regulator and still have the same 20 psi .If i undo the return line and plug the fuel rail i have 35 psi.Please help

Get a repair manual and look up under the fuel rail set up. It should talk about how to prime the fuel rails and fuel lines.

Try a new filter, maybe it is restricted.