So that others may live... Praise the junkyard jeep gods!
So I went over to the u-pick-u-save in pomona today, and found exactly what I was looking for, the same vehicle year, same model (1990 XJ Laredo) with the exact same options package (factory ABS), except this one had the ABS go bad already, and an ABS delete was performed on it.
The booster also looked to be the same one mentioned in the "extra power booster" article I posted earlier (was off a grand cherokee) and also had a very nice aluminum backer plate machined for it, so no spacers needed.
I don't know what the story is on this jeep, but someone poured a lot of love and time into it, it also had what looked to be the factory rock guards (which I grabbed, and will now install on my jeep). Oddly enough, the one next to it (a 1986 XJ) also had the factory recovery hooks, and was similarly equipped with the tank and suspension guards, but someone had already pilfered those parts. (I didn't take the recovery stuff, so it's still there for the taking, and possibly easier since I loosened it. You will need to bring torx wrenches to take off the mount).
I think I'm going to spend the remainder of the day recovering (I got waaaaay dehydrated, and probably a bit heat prostrated), I'll pull it out of the truck tomorrow, pressure wash it, take some pics.