Spark Plugs (again?)

[ROADNOTCA]

So the booklet in the glove box says GM #1259932 for sparks. Shop manual says GM #12569190. We do have agreement on plug gap at 0.042. Autolite says gap S/B 0.040 so I assume they're stupid.
If GM isn't that picky about which plug to use, then I won't mind using non-GM.
I've read that when GM first developed HEI, they tried ~0.060 gap, but didn't get the plug life desired, so they rolled back to 0.040-0.045 etc.
We don't need no stinking 100KM plug life, we need kick-ass from 0.060 gap.
Any other members have experience in this area?