You might want to indicate (in the Swap Meet) the year of the radio you have and year of the radio you want (if they are different years). And/or post photos of the front of your radio's body and the rear of your radio's body (positioning the camera a little above the body and a little to the side of the body). If you are going to buy or trade, you'll want to be dealing with the right years and makes.
Chevrolet Advance-Design and GMC New Design radios changed some over the years (1947-1955). truckernix (and others) know the differences.
Also, I think truckernix has posted that positive/negative did not matter, as long as you do not have a replacement 6v solid-state vibrator (he'll correct me, if this is wrong).
