Running on 4 cylinders

The car is a 1970 Dart Custom
225/904
+/- 112k miles on it

So I’ve been chasing the misfire my car has had since I bought it. Every thing I have done so far has helped, but it is now to the point where I think I have done all I can. The car seems to only run on 4 cylinders.

I pull the spark plug wires and there is no change on #1 and #6. This is very peculiar. I know they are both companion cylinders so it must be something they both have in common.