Have you disassembled the distributor and inspected the advance weights and springs? It sounds like the weights might have rusted and stuck in the advanced position, or a spring has weakened over time, or broken. Can you turn the rotor clockwise with the engine stopped, and have it spring back? The advance weights and springs are accessible by removing the breaker plate, without taking the shaft out of the housing.
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
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