I had this same problem as I’m sure many have. I believe Jerry (Hotrod Lincoln) was the one who gave me a trick which worked. Take an old speedometer inner cable. Clean it really good and start down your headliner. Spin the cable with your hand and it will fine a path. I went all the way from below the dash, up through the ‘A’ pillar, to behind and above the door. Pulled the new wire to there then repeated the process to the top center where the light is located.

Six volt guy living in a twelve volt world