the stock pistons and rods are fine, trust me. unless the valve lift is like .600 (exaggeration) then you wont have to worry. but never the less it would idle like shit if at all and be totally unstreetable.
what you do have to worry about is if your valve springs and retainers can handle the cam. what you'll also have to worry about is when the cam produces power because if its like a set of jun 3's or toda c's then the power extends over the redline and fuel cutoff so you'll need something to do away with that so you can harness your power. not to mention the springs wont be able to take it and you'll float a valve into a piston.