A most efficient highly developed all race N/A motor on good quality high octane race gas will like less timing than a conventional bracket or Stock super Stock like motor will, I'm talking about Pro Stock and Comp Eliminator motors that like a BSFC in or lower than .32 Lbs. per hour
On your deal with those spark plugs it looks like pitting and blistering on the porclyn and way to hot on the heat range as well as rich on the AFR