So now you went and ordered pistons while far as we know you were still looking at the wrong topend? Don't get me wrong the AI 200cc package is the best choice for most builds but NOT for this one. How do you order pistons without a good idea what the chamber volume will be?

Honestly with a NA goal like your's with a combo that also has to have rpm overhead for the 250shot I think you should be looking at converting some altered valve angle SBC heads.

Problem I see is an NA combo that runs 10.0 in a street car is probably going to be geared to max out rpm potential but then you have nowhere to go rpm wise on the bottle. Plus a nitrous converter will be tight NA and soften the launch again making it hard to hit 10.0 NA.