How big of a shot do you plan on running and how often? If its 100> I'd go with stock pistons. Nitrous is hard on a motor, but I think Tom's (now Ray's) turbo has proved that the pistons can take a punishment. Plus, alot of its in the tune.
As for the cams, I'd stick with the SVT cams. The juice will make up for what minimal torque is lost down low.
I think the 11-1 compression is reasonable for the go go juice and pump gas.
