[Arran]

I actually just removed an MP3 player jack from a Westinghouse Columaire 8 radio that a fellow brought me to repair, for one thing there isn't a spot for the jack anymore after replacing the aftermaket IF can with a factory correct one. The owner told me that it never did work properly, and no surprise there, the volume control in this set does not work like a set of a few years newer, it works by changing the cathode bias on the RF, Ist detector, and IF amplifier tubes. In any event he doesn't care about the jack, he's going to get one of those part 15 type transmitters so he doesn't have to screw around plugging the MP3 player into the set directly.
Personally I don't like aftermarket jacks added to radios, I've run into to many amatuerish installation jobs of adding an RCA phono jack to a sets that never had a phono input and always remove them. It's easy enough to find sets that had a phono input straight from the factory to bother trying to make someone's hack job work or messing with the audio circuits of a radio. If you want such an input to work it must be tied into the volume control/avc circuits in the proper way with shielded cable, coupling caps, etc otherwise you will get a load of AC hum and static coming through. It is also unnecessary to drill holes in the chassis to accept an input jack, the jack can be mounted on a plate attaeched to the back of the cabinet fed by a shielded cable going through an existing hole in the chassis.
Regards
Arran