What is the best possible gap to set a spark plug at? Is there different ones for better gas mileage opposed to more HP?

Large gap, small gap..... super excel coil or standard coil...its like standing in a swimming pool of gasoline...one match or a blow torch...the result will be the same......the theroy behind a large gap was or still is , cars run leaner, increase the gap to get more gas particals between the gap. .035 will do well,but the life of the plug will be shorter, no diff in HP

Yeah, if I buy Iridiums I dont want them to shit out right away.

Well, I have had troubles with the platinum and other "fancy" spark plugs out there, so I have never tried the Iridium ones. However, I have always used the factory setting of 0.35 (for a first-gen) on the OEM Champion's (P/N #RC9YC).

L8R,