The "high" cap came out in 1955, I believe, with the swap to a 12 volt electrical system. It's not uncommomn for the center button of a distributor cap to deteriorate if metal core spark plug wires are used instead of the string-core resistasnce wire, but that happens over several thousand miles of running, not a few hundred. Check to see if the distributor shaft is wobbling and rubbing the rotor sideways over the center contact.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!