Damn Greg, what shot are you running? I know guys spraying a 150 all day long with no problems running stock lower ends. Are you retarding the timing when you spray? Something just doesn't sound right. What kind of setup are you using? Forged pistons will definetely help now that you're installing another block but I'd pull the plugs everytime you spray just to determine what's happening and log your pass so you can make the necessary adjustments so this won't happen again. My old vortec lived a long life and the pistons are still good in it and that was a 150 shot 2 to 3 times a week. Richard at Strictly Performance can vouch for that because he filled most of my bottles.