I am attempting to wire a third brake light into the wiring harness from a 1992 Suburban. (It now resides in a 1937 Cadillac). I am using a 1940 Fors tailight as the third brake light; it mimics the decorative chevrons that originally resided on the trunk lide.

How can I wire a third brake light and keep it from blinking when I turn on the turn signals?

Each taillight has a ground, a running light, a turn signal, and a reverse wire. I can plug in the running light wire, but if I use a signal wire it blinks when the turn signal is on. Do I need to run a new wire all the way to the brake switch? If so, do I just splice it in or do I need to find another power source?

Thank you, Jay