Yes, the stock pistons would be cast. You probably need to consider your end result for what you are wanting out of your engine, and base your build-up around that. If you are considering nitrous and a relatively stout engine, then forged pistons should probably be placed into your budget. Cast pistons are fine for daily drivers and can even endure short bursts of nitrous in low HP levels, like dry shot kits, but they are still just cast, and not really intended or designed for high RPM or bigger HP nitrous kits or high turbo boost.
