What a headache!
Finally solved the problem.
Actually a few of them were all piling on top of each other.
In-tank pump & its fuse were dead, replaced, no joy.
Swapped out various electronic components to no avail including the coil.

I had recently (NOV18) rebuilt the engine and had bought new spark plug wires so had dismissed them as a problem source. I did check for sparking early on but did not observe any which reinforced my conclusion they were OK.
Was at Pullapart and found a 940 so scavenged a few parts just in case my backups were bad. While there saw the plug wires were fairly new so figured why not and grabbed them.
Continued to swap out newest acquisitions with no joy.
Thoroughly exasperated by this point I swapped in the used wires.
It started right up.
Joy.
Crappy A-zone wires were sparking only when in contact with the valve cover so sparks were not observable. 5 months old and leaking sparks.
Got new wires (not from you know who) and will install tomorrow (still a regular drop out during idle with the used wires).