If the coil has FoMoCo stamped on it, it's probably time to get a new one.
When I took delivery of the barge in 2002, it had a Delco coil that had exactly the same shade of faded Pontiac blue engine enamel as the rest of the engine - I figured 30 years was long enough for any coil. I replaced it, even though it still worked fine. I've kept it, just in case.