I know there are a lot of threads like this here, but of course my symptoms are uniquely special, just like me.
Basically I can't get more than 50 feet without the car dying, if even that. I've checked all the easy stuff and cleaned a lot of contacts/fuses, and have ruled out fuel supply as a cause of my no start/start-then-die: the fuel pump relay clicks, I can smell gas when cranking, and car won't start any better when fuses #4 and 6 are jumpered and the main pump is whirring (transfer pump may be toast but that's another story)

NO SPARK on a grounded plug and wire (most of the time), but I get one with the Hall sensor disconnected and terminals B and C jumpered as per the manual. Terminal A on this plug has 11 or 12v on it, as it should, and terminal B has its 5+ volts. HAYNES says I need to replace the pickup coil, but other threads say that is some kind of misprint, since the Hall sensor replaced the pickup coil in later models...(?)

The distributor plastic cover (between the rotor and cap) is completely loose, and the plastic base that holds the plug connector there is basically only attached by the three wires that connect it to the ICU. That strike anyone as out of the ordinary?

The coil has power but reads 1.5 ohms too many at the primary circuit. But maybe my meter is just inaccurate. The ICU has power. They are supposedly bulletproof anyways (right?).

Does anything else trump this, or do I just attack the Hall sensor? (not stoked, that will definitely require a mechanic for a guy like me!) and yeah, i have read the FAQ

Anyone's ideas will be awesome to hear, thanks fellas

If you are saying that this plastic piece(photo):
https://www.brickboard.com/FAQ/700-900/ElectricalIgnition.htm#DoesMyCarHaveaHallorRPMSensor

Has broken, cracked, etc. Then the wires to the hall sensor short out touching the distributor. You can buy just the plastic connector that fits in the distributor housing. Just make note of color wire position. Easiest pulling distributor to do this.
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well i didn't take the rotor off, because it is just really on there like a mofo, so i can't say what it looks like underneath the shield where the rotor pokes thru the center (this shield is completely loose itself and isn't clipped into the distributor housing). The loose connector piece that I meant was the three prong connector at the left of the distributor in the photo you posted. It's just hanging on by those three wires.

I would love to get the distributor off but it sounds like a difficult job. Will take another look at it when I get home.

Pulling the distributor the easy way. Gear wrenches, if memory serves, 10mm. Bolts have "stay fasteners" so you just have to back them out and the distro pulls out. Mark the base of distro with valve cover to get a close alignment when re-installing. Yes, the piece I described is the one that will cause shorting out that's hanging by the wires. You don't have to replace the actual hall sensor or the distro. Over time heat, etc, causes the plastic to break down.
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OK thank you! I messed around with it today and got it to start: it acted all haywire at first, and the tach went way up to like 5K (!!!, although I am suspicious if it was actually revving that high). I then killed it, went to my job, and tried again tonite. This time it started fine, so I decided to jiggle the Hall connector while it was still running and BINGO: the car began to hesitate, or revv and get huffy, as the symptoms have been since this started over a week ago. The tach responded to cranking on these times of starting, but I can't remember if they did when it was no start/no spark (pretty sure it was NO).

You're saying it's easy to pull it, but according to the FAQ etc it at least sounds like a real nitty gritty gearhead's job to swap out that Hall sensor at least once the unit is out. I will look for a complete unit at the yards tomorrow. Do you, or anyone else who is reading this, happen to know which of the 740s use the same distributor with that sensor in it? Should I just look for any that match the external description (i.e. a three prong Bosch connector)?

Thank you! Stoked this is getting somewhere! Viva brickboard!

I think you are missing the point. Hall sensor stays in, connector ONLY gets replaced. Replacing the hall sensor is a pain.

Capisco. You guys make it sound so easy though. That plastic clip holder doesn't appear to be built to be replaceable from what I can tell - how can I disconnect the wires and then reattach them? Especially from working underneath the hood. Seems like either I pull the distro and bench fix it, replace it, or else just epoxy the shiztu out of the broken plastic clip holder as it sits in the engine bay.

I pulled a better looking distrubtor from an 87 245 at the PNP today and it was not fun at all - had to remove the radiator just to gain access to a place of purchase on the engine block with which to pivot off of for levering it upwards with a wrench, since it wasn't coming up just by pulling. Those manuals also make a laughingstock of how difficult it is to remove; i think the only thing capable of pulling that out on its own is an engine hoist. My last resort is just putting this one in there but I am not sure about getting the timing right with the cam, etc. Let alone just getting mine out without draining and removing the radiator.

Gonna epoxy the clip holder in place tomorrow and see what that does!

Didn't pull and bench fix the distro's Hall wiring receiver clip, just ziptied it into place for temporary solve once it was clear that it wasn't going to affix to the housing by epoxy. (Maybe I didn't properly clean the surfaces, or maybe I used the wrong epoxy, hard to say, it is not something I've much experience in). Going to cinch it down around the distro with a hose clamp very very soon.

This, and this alone, has gotten the brick SS Blue Meanie back to starting on a nanosecond crank and purring along like the ancient beast that she is. It is not any fix worth paying for, but at least I can get to work on time now. The spare distro will come in handy for whenever I feel like doing this by the book.

Thanks alleecat and Unkel Udo for the straight talk. I apologize for the thinking aloud.

BTW you were right about that clip being replaceable. IPD doesn't carry it but it be sourced online.