Dave,
Original plug gaps for HEI were reduced by GM from 060 to 040-045 because it was so reliable, didn't need tune ups. Cars were running for 000s of miles with the plug tips eroding & increasing the gap. The cheap carbon leads etc were also the cause of the problem.
If you read this forum, it is 'powered' by enthusiasts.....people who buy the best parts they can afford for their 'baby'. That would include good quality ign parts, such as spiral wound HT leads.
You seem to have missed the same point that that idiot Rat Bastid missed: power means everywhere from idle on up, not necessarily peak power. If you read my earlier threads, I have given examples of power increases in the mid range from 060 plug gaps.