I have a very good radio man as a friend who has done this for so many years.. he made me a 12v version of the original radio by simply changing the filament tubes and a few other things. When asked about what antenna should I use and NOT have any holes in the truck, he said to take about 60 inches of copper wire and wind it around the bottom of the running board. Insulate if of course from any metal, and use it as an antenna. Nobody will see it, and it will work every bit as good as the hole in the cab version.
