Beware of some of the parts store flywheels. A customer of mine had two in a row that lasted less than a year. They both cracked on him. They are very cheap but maybe you get what you pay for. I know the OEM flywheels are not cheap.
I used to have a good original used one. I can check but I think I sold it.
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1966 Strato Chief 2 door, 427 4 speed, 45,000 original miles
1966 Grande Parisienne, 396 1 of 23 factory air cars (now converted to a "factory" 4 speed)