Strange idle issue

Last few times I drove the car (67 Dart), it started fine. Drove it 5 miles or so, shut it off, 5 minutes later restart it, idles about 700 rpm. Normally idles at 850 rpm. Driving back home (5 mile return trip) it has a definite miss. Could be a spark plug, BUT, I get home, leave it idling and open the hood to check a couple things. It isn't like the engine is just shaking real badly, but it is actually a little more stable but idling lower. There is fuel in the holley carb bowls. As I am looking things over it is idling lower and lower until it just shutsoff. During all this the AFR gauge is showing extremely lean when idling, so lean the digital gauge pegs out and wont read. Advice needed.
ALMOST FORGOT. Car is YELLOW