Missing on 3&4

[Ken Canada]

Hi, due to a bad radiator I overheated my engine. Since then the engine does not idle properly, when I remove the lead to either spark 3 or 4 it doesn't seems to make a difference in the engine idle. Below is what has been done
- no cracks found on block or head
- valves appear to seat properly, open and close properly
- new head gasket (60lbs across all cylinders)
- swapped out distributor with a known good one (off my other A)
- checked for any intake leaks (I sprayed ether around intake no change)
- swapped carburetor from the other model A
- changed plugs
- double checked propre gap on points and new plugs
- changed coil, even though we had good spark

The engine runs strong and does not seems to be missing when driving at any speed. Just when you go for a stop the idle seems to be missing. I assume on 3&4 because of the test of pulling the leads on those 2.

Today I pulled the head off again to check for cracks or anything, but I think I'm at a point were I'm going in a circle and maybe some fresh in-site or comments may help.

Thanks in advance for any help in solving this puzzle.

Ken