1998 4.0 code P0351, engine died

I was ten miles outside of Reno and not quite to Truckee doing 70 mph when the engine died. Not a sputter- it was like flipping a switch. Pulled over, turned on the blinkers. Took a wild guess and said to myself "Thermal failure! Crank position sensor!". I always guess that and I haven't been right yet.
Anyway, I wait a little bit for things to cool and try to re start it. Cranks just fine and I can hear the fuel pump kick on but I get no ignition. Check for codes, P0351 - Ignition coil primary circuit.

OK. So it could be power to or from the auto shutdown relay (B+ supply to coil) , could be the PCM, could be the ground wiring from PCM to coil, could be the coil. Most likely thing, if I can't see any obvious problems in wiring, is the coil. I'll check the wiring anyway and check for power / pulsed ground while it's cranking.

If the secondary wire (to the distributor) needs it, I'll replace it.

Anything else I should be aware of on these motors? I think I've got a handle on this one but damned if I wouldn't appreciate a second opinion... What say ye?

I think you've got a very good handle on where to start.

I've only seen this code one time on an XJ and the problem was the PCM. But certainly verify wiring, connectors, relays, coil, etc. first.

I should see B+ voltage at the coil with key "on" but pulsed ground only while engine cranking / running, correct?

OK, tested it out according to FSM (check for spark in coil-to-distributor cap lead, check continuity from PCM connector to ground & to coil, measure primary & secondary resistance in coil, check distributor drive, check mechanical valve timing, check resistance of coil secondary lead, etc) and came up with "replace PCM".
Did a bunch of homework online (IATN.com) and came up with "replace PCM".
So, I guess I'll replace PCM. The coil has some cracks in it, so I'll probably replace it as well - though I don't expect the coil to fix it. Secondary lead from distributor to coil was a little funky but tested in spec. I'll replace it, too, just for the hell of it.

Will post findings when I have some.

OK.
I re-did all the battery mains for fun & replace the PCM.
No change - car cranks but doesn't start.
I get no spark. I'm basing this on having put a timing light on the secondary wire from coil to distributor cap, pulled the trigger & tried to start. No flash.
I can hear the fuel pump turning on when I crank / cycle the key.
With key on, I get no power to coil.
When cranking, I got ~10 volts (remember, it's pulsed ground, so it won't show a full 12.5 vdc) at the coil going across the ASD output and pulsed ground. I'll do this test again when I have a helper.
Coil primary and secondary resistance are in spec, though there are numerous cracks in the plastic / epoxy housing. No evidence of arcing, though.
Crank position sensor reads 2.1x mega ohm across terminals B&C, which isn't correct, but I think I'm getting signal to coil anyhow so not sure if this is relevant.
It died all of a sudden, didn't seem to stagger or sputter. I get a puff of pressurized fuel when I tickle the test port. Not as much as I'd expected but it does get fuel pressure and the pump turns on.
So...
What else am I looking at? Buddy is theoretically coming by with a coil for me (I'm stuck with no car at the moment and I'm sick enough to stay off my bike) in a bit. He's a better mechanic than I am but neither of us are Jeep specialists, really.
So, what else should we check out?

Update / Summary :
Replacing the ignition coil fixed it.
Though the old coil tested good and the DTC stored almost always, from what I read, means that hte ECM is bad - it was NFG in reality.
Oh, well. $35 for a coil, $75 for the ECM - I'm still getting off cheaper than letting somebody else deal with it.
Lesson here is that a refined sense of intuition and likelihoods is some times more valuable than reading the FSM.

Edit: Nevermind you fixed it.

All good advice, Jon. Fixed it 10 minutes ago, though. Coil was it.
Now to wait on the next problem...