Misfiring / stuttering issue

Check that charging system real good. Anything that affects the voltage to the primary side of the ignition will be exaggerated on the secondary side. Too high voltage is just as bad as too low in the ignition system.
It's been documented & discussed at great lengths here about the electrical troubles on these cars at the bulkhead connectors etc so I won't go into that now. But well worth checking out.
Also make sure your points are in good condition & all electrical connections there & at the coil are tight & not shorting against anything.