There's a fairly nice looking 91APB1 (AM radio) on
EBAY right now for $250 plus shipping (or best offer) that's been refurbished with a 6 month warranty.
There's also a
REALLY nice looking refurbished 91BFP1 (AM/FM mono radio) on
EBAY for $1300 complete with the bracket, knobs, harnesses, speaker and even the U80 rear speaker option!
You could go either way and still be "correct". Heck, if you really wanted to, you could even install the AM/FM stereo but it would probably cost at least double if not triple what that AM/FM mono is on ebay. You'd have to source all the parts required, but it could be done. Some of the parts are being reproduced, so mostly just the radio and the 91FMP11 multiplex would need to be found. I think all the rest is being reproduced like the harnesses, speakers, speaker covers, etc...
Ed