Good Morning All, I suggest using AC45TS (they are not to long unless you have domed piston which you do not) and set gaps at .042 instead of .045 as recommended by the books.These are used for continued street use (start and stops in city).. For performance engines that run the track or is used on long road trips at high rpm we use depending the use i.e. strip use AC42 TS series,next hotter plug is AC 43 TS,for combination some street. For freeway(California folks) use AC44 TS.Daily driver with an occasional highway drives use AC45TS and all with the gap of .042. I have evaluated all these on various engines and race cars over the last 30 years with much success. As far as octane of fuel,unless your engine is timed at 4-6 degrees advanced you would want to use at least 89 octane,however I did a study on my '72 Chevy 1/2 ton pick up with a 360 hp 350 engine and found that while burning premium fuel I burned less fuel (15 MPG as opposed to 12 with 89 Oct.)   I would not consider burning 89 in my (370hp 350) Vette and in fact I have located a couple of service station that have NON ethanol fuel..That's just me and all the people here that I have built performance engine. Have a great day and happy motoring...Sal C