[ford38v8]

Rich, your travelling air bubbles most certainly prove an air leak. The rapid loss of pressure after shut-down is an unrelated issue, and not necessarily a problem anyway. The most common source of air leaks are at connections, of which you have a pretty fair handful. Starting at the rubber hose clamps, replace any that are NOT worm drive clamps. For the life of me, I don’t know why spring (garbage) clamps are still furnished with fuel filters and such. As with radiator hoses, always tighten over a couple of days, to allow the rubber to compress and form a good seal. The next most common are at the mechanical pump gaskets. Pump castings warp, gaskets dry out, threads strip out, ferrules, tubing, and fittings need freshening up. All these on the suction side from tank to pump are suspect in producing air leaks, invisible, as they leak air in, not fuel out.