I'm getting ready to send my '55 Selectronic radio into him. He really knows his stuff on the old Buick radios. He quoted me $110 to basically replace all the capacitors and to go through it. You might give him a try.
If you are looking to upgrade to modern electronics (AM/FM/Aux input) but keep your original look I'd suggest checking out the folks at Antique Automobile Radio (URL=http://www.antiqueautomobileradio.com/). They take out the old tubes and put in modern electronics.
They did the radio for my 56 Roadmaster. Looks like an original but now I have FM and an input for a CD player. Depends on what you are trying to achieve.