93 I also have the FSM for here (picked up all the 92-94 ones off RockAuto when I was considering a Magnum swap, so I'd have all the wiring diagrams. RA no longer shows them, alas, but Bishko has'em for under $40 so not a big problem IMO.)

I find it going to Circuit K on gauge PCB, pin 6 of Transmission OD switch (page AN27), transmission oil temp lamp (page AN22), dome light (page AN37).

I'd start with unplugging the dome light circuit. If it's only when the motor is warm, maybe the transmission oil temp light in the cluster first.

RwP