Heat range is defined by the number (44, 45, etc.) Even though the porcelain is different, if they have the same number, they have the same heat range.

For emissions, they tried to do .060" gap with HEI for better combustion. But with low compression, once the plug starting getting some carbon buildup on it, sometimes there just wasn't enough energy to jump the gap. This caused misfire, so for this reason many gap to .045" regardless of which type they use.