Thanks for the thought. Turns out air in the lines before the injector pump but after the lift pump. It bleeds right in between at the fuel filter schrader valve.
It took a while after all the air came out, but started and got run a few miles yesterday. The big question remaining is whether I can start it up today or have to go back to bleeding the line (which means crawling under and connecting a manual starter switch to the starter solenoid) before each startup. That's just a little too much to live with.
So, in the end the electrical connections to the fuel pump cut-off mechanism didn't seem to be the cause at least this go round. I'm thinking for short intervals (say a week or two) the fuel lines leak air and for long layoff intervals (say a month or more) it's more likely corrosion on the electric connections at the injector pump cut-off solenoid.
Hope no one else has to deal with this. Truck's too old to run right but too good to junk.