Another try if you want to do a digital am/fm conversion, but keep everything else, try Mike Frenchek at the following:
Retro Radio Restoration I had him do a thumbwheel Mopar radio and it works fantastic now -- EVERYTHING works on it, and I have RCA plugs in the back of the radio that I use to plug in my iPod -- so I also purchased an iPod interface, so now I can listen to it as well as charge it with the older plug in. Wasn't cheap, but I would do it again -- like I say, it really works and it looks stock in appearance as nothing else is changed, other than the guts of the radio that you don't see anyway.
Best of luck!!!
Mark