The design of the radio relied on the chassis being grounded to the case. The tuning assembly is grounded to the case by a soldered braided conductor.
With regards to testing you can power it up with the truck battery through a fuse, (10 A or so). You can use a piece of hookup wire, say six or eight feet long for an antenna. Just bare a bit of the end, maybe double it back if it is too thin and insert it in the middle hole of the antenna socket. Some radios with the electronic vibrator do better with the higher charging voltage, around 7.4 volts. If you are in a steel clad building, you might want to test it outside.
