Unless you're going to run high-compression or forced-induction, there is really no reason to use premium gas.
It might be helpful to know what
Octane is first.
For spark plug gap you'll have to play around with it since you are mixing and matching parts. I've mention this before in the other thread, Move up .010" increments till you get misfire under load (or you feel comfortable with) then lower it by .05".
I use Autolites. They are the basic ones. I've used platinums before and noticed no real difference other then them costing more. I've used Accel U-groove plugs, Bosch Platinums, Bosch regular and Champion regulars. The only ones that I have tried are copper plugs like the Champion Truck plugs and NGK Iridiums. The NGK's are popular on many higher compression engines. They cost more though. I think you'll see a bigger difference from optimizing your gap then getting a different spark plug though.