[hatzie]

You only need VSS when you have the serial data from an ECM/PCM of the correct generation to run the MPG calculations. I doubt the compass uses this wire. I'd leave it as stubbed off pigtail with some heatshrink over the end. Leave enough wire to attach it to a wire from a VSS if needed.

INT Lite DIM #9 is a feed from the instrument panel lamps to dim the digital display depending on the voltage level from the headlamp switch. Fun but strange fact the 73-91 squarebody trucks used Gray for the instrument panel lamps.
The parking lamps no doubt signal that the nighttime lamps are engaged so the display dims somewhat with additional input on how far to dim from the instrument panel lamp wire. The 73-91 trucks have at least one unused position on the headlamp switch plug and switch that's tied to the parking lamp circuit.

Fused BATT is #14 Orange

The swiveling dome lights are wired separate to the dome lamp wiring on the 90's & 2000's trucks as far as I know. The dome in your cab is fed fused battery voltage all the time and a switched ground from the doorjamb and headlamp switches. I would pull the ground and power wires for the two lamps in the console from your dome on the back of the cab ceiling. You can probably use the dome lamp power for #14 on the compass/temp module.