Attack of the Corrosion Beast!?!?!
Clint,
I have similar problem on my '77. I think it has a lot to do with the age of the cars and slow corrosion deposit build-ups on the connectors in the electrical system over time. Every connector I have pulled in the last two months (about 7-8) have been white with corrosion. I just replaced the lead to my starter yesterday and - oh my what a difference that made! I would suggest that you start pulling injector clips and hosing them off with electrical contact cleaner along with the other connectors under the hood. It is a daunting project, though, because the connectors are old, brittle, and buggers to get off without breaking them!
You could, of course, just live with the miss at idle if it runs OK at all other RPMs under load.
OH yeah, if you have a volt-ohmeter (that's a VOM for Doug Dawson) you might check the resistance of your spark plug wires. Measuring from the contact inside the distributor cap to the end of the wire the resistance should be less than 30,000 ohms.(30K ohms for Doug) If it measures more than that on a wire, measure just the wire itself and see if the problem is in the wire or in the cap. You could be loading up on one wire over time.
Phantom