Courtesy light / dome light wiring
If its any help, on North American A-bodies, the dome light gets power from the same fuse as other 'altways hot' lights.
The actual location of the junction varies.
1967 (except maybe fastbacks and 'verts) it was done at the headlight switch
Yellow is the earth side going to the on/off switches - one in each door jamb and one in the headlight switch.