Well in that case, try grounding the temp sender out and observe your guage. Is the guage pegged hot? If not, may have a lost or broken wire going from the temp sender, a lost of broken wire coming from the ignition switch, or even a blown fuse.
The temperature sender is a gas charged unit. After 50 years of use it is not uncommon for them to stop working. Replacing the sender might be a next step. If the test above worked, and made your temp guage pegged to the hot side, your temp sender will need to be replaced.
