I have the 198 rods in my possesion for a new motor it will be drag race only. Which of the KB pistons the KB268 dish or the KB 239 trench valve relief Is a better starting point for a normally aspirated engine in terms of arriveing at valve to piston clearance. And maximum compression?I relize there are many variables. The cams will be.500 to .550 lift 250 duration at .050 108 or 106 c/l. Are you better of ordering custom pistons or can these pistons be made to work? Thanks for your input and knowledge.