.1990 GL  2.1 with 260k + (120k on a boston bob overhaul)

  I've been keeping a fuel pressure gauge signal going to my VDO oil
pressure gauge(toggle switch to change sources) and for several years it
read right between 29-36psi  just like it should.  Then about a year ago
it dropped down to fluctuating to a reading like 17-20 psi.  The engine
still started and ran okay, but within the last couple of weeks, i've
run the gas tank past empty on two different occasions and had to
reprime the fuel lines and bleed the air out of the lines from the test
port screw.  That seems to be the onlywlay to restart a totally dry fuel
system.  The second time it ran dry, repeated attempts to bleed the air
etc. have proven to be unsuccessful i ngetting it to start again

I realize that running the fuel pump with ho fuel for lubrication is not
good for it, and my spare used pump when installed leaked fuel out of
the crimp at the top, so that wasn't an optio.  Before I spend mega buck
on a new pump, I;'d like the list's thoughtson where I go rfrom here.
Could the fuel pressure regulater be causing these issues of no pressure
at all?  Is there a chance there's still vapor lock" in the injection
lines downstream of the test port preventing fuel from getting to the
injectors.  The engine will cough when ether is briefly shot into the
air horn, so it's not an ignition or compression issue.  i have a known
good used regulator, but I'd like a bit of guidance before I do too may
spendy things to get it roling again....and yes, there 5 or 6 gallons in
the tank right now.

TIA

DM&FS