It looks like a combination of the two as you suspect.
That bit about running on 2 and 3 cylinders is common to one side of ignition system not reliably sparking as they are separated for those two and successively 1 and 4.
Coils on these are generally very reliable so wouldnt be prime suspect. It's worth going through points and the small insulation washers where the wire connects to them, then making sure the wires to coils from there are connected with decent continuity before judging the HT section. That may bring up something, and of course points gap / timing.
Carbs you can synchronise mechanically as a reliable method not dependent on running to give you baseline in that respect
http://www.sohc.co.uk/index.php/topic,17769.0.html will get you plenty accurate enough to take that concern out of the equation.
When they've been sitting a while you can chase carb cleaning through a number of times before you get them sufficiently and reliably clear enough to run competently.
One method of carb diagnosis is if a cylinder is not obviously running, then remove the synch screw and spray carb cleaner in there with a tube. If it chimes in with that it indicates a jet blockage. May help you seperate the cause as no response points to ignition.