[bestgenman]

Dean,  I have serviced hundreds of DD over the years and the fuel system can be very problematic.  The lift pump has limited ability to suck fuel if air gets trapped in the gears and surrounding cavities.  For that reason, we never removed both filters at the same time.  For those not familiar, the primary is on the suction side whereas the secondary is on the pressure side.  We would remove/replace the primary, start the engine to remove any trapped air caused by the filter changing, and let in run for a minute or two before changing the secondary.

Since you replaced such a long section of the plumbing, it is highly likely some air remained.  The pressure gauge is a great diagnostic tool.  The pumps work well as long as they are flooded with fuel, tHe suction side gives the most problems.  Detroit pumps act differently than other gear pumps for some reason.  Cummins PT gear pumps would lift fuel several feet with just a drop or two of fuel.   Series 60 pumps work well also but here again, the filter is on the suction side and air is your enemy.

I know you likely already know all this rambling so, I hope it helps someone else.  

BTW, nice paint job. ?