My understanding is that on the tube type radios polarity does not matter at all. I've not tested that, and haven't asked anyone who would really know...

Click here for pictures of a '54 - '55 1st GMC radio. These are NOT dial-up friendly pictures, but are high res shots I took when someone was interested in my GMC radio.

1955 1st GMC Suburban | 1954 GMC 250 trailer puller project | 1954 GMC 250 Hydra-Matic | 1954 Chevy 3100 . 1947 Chevy COE | and more...
It's true. I really don't do anything but browse the Internet looking for trouble...