What they used: nothing was available for 47-55 trucks - "in the day".
The original light/lamp switch provided a ground to the bulb. The lead/wire to the housing is always hot to the "normally" ungrounded bulb. A ground (turn/flick the switch on) is needed for the bulb to light.
When other cars/trucks had/have a switch, it was a spring-loaded button in the door jamb, providing an on/off switch to the lamp housing.
To make that work with your original housing, you could run a ground-lead from each door and connect both door leads (from each/both side/door) to the switch in the dome light housing.
Let's hope someone will correct/chastise me, and will provide an easier "solution".
