[DaveA]

This sounds like it could be weak distributor advance springs, or a sticky distributor advance. If the advance mechanism does not pull back to zero at idle, it will cause the engine to run fast. Pull the distributor cap off, and work the advance by turning the rotor and releasing. Pull the rotor off and add a few drops of oil to the felt in the middle of the rotor shaft. Finally, check the advance with a timing light to see what is going on.

R/Dave