Troubleshooting stumble at idle in gear

I set the idle at 750 (in Park) per the 1974 fender sticker. I realize that might not be optimal in the current build, with modern fuel etc, but I don't know of any reason to change it. Anyway, it's been running well for the last couple of weeks. There's still a slight hiccup when it's idling in gear, and I plan to continue troubleshooting that (had to buy a new timing light when my old one quit lighting up). But it's not stalling at all.