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by Art Isaacs
Most of the radios for the B were either dealer or owner installed or in the least were replaced over the years, so to say definitively what type you have, how the wires are run, etc. would be at best a guess on my part, so you will not know what you have until you remove it.
Having said that, for the most part, the antennas have permanently attached wires or connections unique to that brand, so plan on having to snake the new antenna wire to the back of the radio. The old antenna should remove from the top of the fender without needing to get beneath it. I usually cut the old wire off the base and then use it to pull the new one into the interior. One trick is to put the pin tip of the new wire into the center of the old one and use electrical tape (thinly spread over a length of the old and new wires) to hold them together and gently pull the old wire into the interior with the new one following. You can also attach a nylon cord to the old wire and pull it through from the interior and then use the snaked cord to pull the new wire back.
You can get between the front fender and body (just barely) by removing the splash panel, a filler piece attached inside the fender to the firewall on one side with a rubber gasket to the fender on the other, and that gives some narrow access to the gap between the inner fender and body.
Removing the front wheel allows you to get in enough to see
the space, but it takes thin hands to retrieve anything from there.
Most B radios, even with post-type tuner and volume knobs, are the more modern DIN mounts, meaning they pull out from the front of the console making it easier to remove and connect wires without having to remove the console itself. It also means most current aftermarket DIN mount radios can fit without modification.