help-popping up through carb-seems to be dist/cap/rotor issue???

Ok- I have a 74 Duster with a 78 360 4 bbl. My car just started to pop up through the carb a while ago. I thought and was told by many that this is a cam issue. Makes sense and sounds like it would be. Then my dad says-check your cap and rotor, replace them. ok ok, here it goes- a few months ago, I bought new/reman distributor and new cap/rotor/ wires/ and plugs. Ran great. A few weeks later-popping through carb. High mileage engine-so goes to make sense that its the cam. It would pop loudly around 2000 rpm-whether in idle or in gear.
Today- I replace the cap and rotor. I can rev up to atleast 3500 rpm in nuetral with no popping sounds heard. When in gear- it still "pops" around 2000 rpm but not nearly as bad. Now when it pops- it doesnt sound like a piston is going to explode. I bought BWD brand cap and rotor-same as last time. Thing is this time- I cant seem to align the cap on right- that square chunk out of cap is supposed to align with the metal tan on distributor-next to the hold down clip. The cap is 180 off, no biggie-seems to not move any and its still aligned with spring hold down snaps. When I took off "old"-only old by about 4 months??-rotor and cap- there was a brown tint around the metal band on rotor where rotor button goes up against from dist. Maybe burned?? arced?? whatever.
Seems like I have arcing going on inside my distributor and cap area. How do I fix? All this was replaced 4-6 months ago and worked great until 2?? months ago when I thought it was the cam.
I have my distributor advance hooked to above port on my eddy 600cfm-the left front port as you are looking at it standing in front of car. Idle seems to be just a little high-1200 or so??. Feels slightly cammed at the stop lights, but timing is good-close anyway. Not sure what else to say on here for info. Could something be bad like a coil? volt reg? the electronic ign unit? distributor?