I'll guess...Mazda B2200, around an '87, '88? I had a '90 and the tail light wiring was distributed independently for function, IIRC. I have a manual, I'll check the schematic.
Edit: Checked the manual, '86 and later models: Backup lights-27W, turn and hazards on one circuit-controlled by combination switch-27W, stop lights-controlled by brake switch-27W, Tail and side marker & license light paralleled, 8W,6W. You should have four power leads compared to somewhat standard trailer wiring of three power leads and a ground.
