I ran Splitfires on my slant and she loved it, Ran Bosch Plat's on the 70 R/T 440 and she stumbled, took her back to Champions and she ran like a champ....I currently have Champions in the 69 R/T now and have 12YC spares. They seem work just right with my combo....with the 509, eddy, dual quads and a hotter cam I am going with NGK