I agree with the Holley carb swap , most Edelbrock carbs are boat anchors they are either right or not right and if they're not right you can forget about getting it right so do yourself a favor and invest in a Holley you'll thank us later.
I would defiently drop your plug gap down to no bigger than .035 I had a simialr problem on my race car and and went down to .032 and wolla, no more misfire.
Also not a big fan of accel plugs either, I know some people use them for header clearance but if you can get away with not using them I would.
I like the A/C rapid fires and the ngk race plugs myself.
Goodluck, Charles