Usually aluminum heads on BB Mopar's act like they've lower the compression ratio one full point and increase the heat needed on the detonation thresholds when compared with the same compression ratio as used in iron headed motor.
My message is BB Mopar usually like a little hotter plug than colder, especially on the street. Colder plugs will be darker, perfect plugs (heat range, ignition timing and dead on air fuel ratios) from a well tuned motor should look like they are almost new.
You need to watch yours and see if they are going black, brown or lite tan under normal light throttle street driving
If their dark looking, use the next hotter plug
On your deal I would use NGK # 7 or the Autolite 3923 or maybe the next hotter 3924, Champion RC9YC ( I think, hope , that is the correct # for 3/4 reach with the 5/8 body size ) should work well also
Do you know that there is a federal law that can put you in prison for up to 10Yrs for using leaded fuel on the public streets if you are caught and convicted?
That is the main reason I switch to E85 on my race cars and hot street cars