Emerson 540A restoration

[Jeffhs]

What is the best (or safest) way to connect a polarized line cord to an AC-DC radio or TV currently using a non-polarized one? Every one of my antique radios, including the Zenith H511 on which I replaced the line cord, has a standard cord and plug; the latter can be inserted in the wall socket both ways, which could create a shock hazard if the plug were inserted such that the hot side of the AC line was connected to the chassis. However, the Zenith radio, and all my other AC-DC antique/vintage sets, seem well enough insulated (if the back cover is well secured to the cabinet and the knobs are snug enough on their shafts that they cannot be removed without pulling on them) that this doesn't seem to be a problem. I am only asking about the polarized plug so I will have the information available if and when I eventually decide to replace the cord or plug.

Thanks.