Al, I think I've seen a picture of this car someplace recently, something familiar about it. I think what we're seeing is the left tail light, so there'd be a right to match. If I remember the leg attaches to the side of the frame rail. Could be a '37 Ford housing too, I think they're less "pointy" than the Chev's.

Hopefully the owner will come back and show us more. Pretty cool.