yes and although both are acting different, both could still be moving improperly. As mentioned, would be good to see what needles you have and watch the pistons when you apply throttle.
The interesting part is that it backfires out of both carbs. Not a lean condition in just one set of cylinders. (1,2,3 vs 4,5,6)
couple other potential culprits.
1) Make sure you have no vaccum leaks and that both Vac and Mech advance is working. I'm sure you have checked this but never hurts to check 3 times. A vac leak is of course going to cause lean cond and not allow and changes you make in the carb tuning to take effect. Don't only check the hoses. There are so many intefaces to check compared to other engines (car to insulator blocks, blocks to intake runners, intake runners to manifold, etc)
2) If you think that you have a non-stock cam, do you know if it is degreed right (Cam timing)? Did the car ever run right? Wonder what kind of overlap you have.