os a3 plugs and byrons 20% on a small block....os 8 on a big block...however I've talked to folks that run os 8's on everything and some run os a3's on everything...I've also heard good things about mccoy 59's....personally I wont run 30% nitro due to engines wont last as long...yeah they may go faster but not for as long...if I wanna go faster I put a better engine on it or tweek the gears...