Fred DiMatteo's former '91L has such wiring. I'll be looking it over closely in the coming days (it's the one with the bubbles and coolant loss). I hadn't expected to include the wiring in this particular examination, but what I find, I'll report here.
Looks like yellow or yellow-black wire is for running lights, Lt Blue-red wire is for left turn, Lt blue-yellow is for right turn. Brakes/turn are on the same wire so it should work on the same 4 wire system as the trailer.