It seems like the points need to be set to .18 on "used" and .20 on new ones for these engines. (At least that's where they're supposed to be on a 216, and the ignition isn't THAT different between the two.)
My points were set to about .24 when I got the truck, and she was doing the same thing. After replacing, plugs, wires, and the condenser, I went in there with a feeler gauge and set the points at .18 (per the shop manual) and I was golden. Runs like a sewing machine.
Try it at .20, since the points are new, and if it still does it, try bringing them down to .18. If that doesn't do it, Try putting new plug wires on it. You may have one that doesn't work.
