OK, replaced the alternator and the three idiot lights went out. So, as consistent with some other posts, when the brake, A/T, and battery warning lights all start to light up or flicker at the same time, irrespective of what the voltage gauge shows, it is an indication of a bad alternator or voltage regulator (which is in the alternator).

It remains interesting that there was no indication of alternator output-- when all electrical items were turned on, no dimming of headlights even with brights and fog lights on.

90 LWB RS: 3 L/mt, JBaker springs, bushings, swaybars. KYB shocks tweaked, 134k mi, original owner.
97 LWB SR: SOLD Sep. 2014 131,006 mi: running boards removed, BFG 31x10.5 AT/KO tires, Air locker, AirLifts, KYB shocks, Cibie fogs, 3rd owner.