Spark plug questions

In response to post 26;
One time, back in the early 80s, I was doing a tune-up on a Chevy pick-up. I cant recall the year of that truck, but I do remember it was HEI. Anyway I put a set of Champions in it;direct crossover from the emissions tag.Well that thing ran terrible. Remember I had just done the ignition; wires plugs cap, and rotor.And it wasnt running bad when it came in. So after reviewing my work and finding nothing wrong, I decided to put the old plugs back in. Like a charm, it ran nice again. Well I zipped over to my supplier and got some A/Cs. Installed those and she ran just fine.
Now, I cant really fault the Champions cause they work very well in all my Mopes.It might have been several bad Champions. I reasoned that was hardly likely. But ever since that day, in GMs I only put A/Cs, Fords get Autolites, and Mopes get Champions. I cant say right or wrong. Its just what I do. Never had a problem since.