I had found an OE GM brake light unit that could easily be installed inside the car at the top of the rear glass, bracketed off the steel headliner edging piece. Then hit an obstacle with that plan in discussions with a technical inspector for the licensing authority; as the car will have Soft-Ray tinted glass, he believes a red light passing through the green tint will be a problem. Never considered that.
So, the options are:
- Use clear glass.
- Find a lamp unit that mounts on the exterior (yuck visually, and no way am I going to drill mounting and wiring holes!).
- Ditch the idea altogether.