Thanks, 

If the socket hanging down has 1 wire going to it, it has to be grounded for the light to work.  Have you checked all the bulbs?  It's possible they are all burned out.  Don't laugh, I have seen it when I worked on cars professionally.  They would go out one at a time, and suddenly when the last one goes out, people realize they don't have dash lights.  I think the radio light is wired through the rheostat, so that would indicate the rheostat is working.  Unless someone has changed the wiring in the radio, like I did my T-Bird.

John

Thanks for the pointers.  I had the thought in bed last night, that as John mentioned, the bulbs could all be bad.  Good idea to watch the radio pilot light while adjusting the rheostat. I'll try that and replacing a bulb.  I think that it is appropriate that it uses #57 bulbs.

Thanks again, 

The radio light is totally separate from everything else, and not affected by the rheostat.  It must be wired directly, it turns on with the radio, even when no other lights are turned on.  I grounded the bulb housing on the bulb with the short lead and it didn't light.  I think I'll concentrate on trying to go to Columbus.