I'm trying to put together a mental picture of the circuit - there's a hot lead that goes through the headlight relay with both the left and right headlights on the same terminal, then splits before the bulb-out relay, then through the fuse panel, then through the harness to the headlight locations? Is that somewhere close to correct?

No. The headlight relay should only have one output, the bulb failure sensor only has one input. The bulb failure sensor is what splits the power. Thus I'd consider the bulb failure sensor (the front one anyways) the prime suspect.

From the BFR it'll go to the fusebox and then to the appropriate A-pillar connector. From there to the headlight. Check the big A-post connector on the passenger side (page 10 of the wiring manual).

I've found, at least with my 89 760, that the colors aren't necessarily going to be spot-on... hopefully it'll be close enough.

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alex