The engine harness was incorrect for his car. I located an 87 GT harness, added a Mass Air wiring extension, tied it to the PCM, got the harness laid in the car and the pump now works properly.
I have to get everything cleaned up and put back together but I can get the car to run and start (plus prime the pump). It's got a bit of a driveability issue that I'll tackle next. The vacuum lines are brittle and some are broken so I'll be fixing that and cleaning them up.