Plugs #1,3 and 2,4 fouling

I would unhook the choke wires and wire the choke open and see if it's the choke.
If this does not fix it ,then i would lean the primary fuel ratio on the carb.
It's the carb ,but what part of the carb is the question.
I had a electric choke on a holley carb before and i hated it.
The choke just seemed to darken the plugs to much all the time no matter what i did.
I don't run a choke on any of my cars anymore, because when the carb is set up right,you don't really need one.