Finally had a chance to break open the parts boxes and install the ignition module. The car failed to start a couple more times, but reponded to the ignition switch being tweaked a few times. Took a bit longer than predicted, but once I figured out access to the seven million screws (OK, only six; 5 torx, two sizes, and one allen set screw for the wheel tilt lever) that hold the bottom cover for the steering column, everything went smoothly.

Could not, for the life of me, find the rear bulb failure relay (if there is one), so I will call Volvo again and reconfirm the part number. BTW, a quick way of diagnosing the relay is to take both rear taillight bulbs out. If the bulb failure light on the dash remains lit when the light switch is in the first (parking light) position, good chance it's the relay, especially if you've cleaned the contacts, etc. to eliminate a poor contact. A suggestion via my Volvo mechanic friend back in Illinois.
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John Shatzer, '92 965 @100K; one of a few still in captivity.