tuning a magnum

Update.... i switched from ngk to autolite copper core plugs, changed the powere valve from a 6.5 to a 10.5, switched my mechanical advance springs from 2 blues to 1blue 1light silver, set the timing at 18 initial 33 total and checked my fuel pressure at wot. took it on a test run and smoked the tires in 3 gears. I pulled the plugs right after and the front half still look brand new while the rears are a light tan. the car still had a very slight off idle hesitation and a slight high rpm stumble. but much better than before. i think I'm on the right track here. going to up my jetting from 70/78 to maybe 72/80 and put a lighter spring in the secondary pod. hopefully the weather holds out another day. thanks to all that replied.