Depending on your deck height and how much the head was milled, you may need valve pockets machined into the piston. You would have to lay it up with some modeling clay to know this for sure. If it's the larger diameter rocker studs, you should be fine with stock rockers. If you're spending the money to put something with nice parts together though, why not install some nice roller rockers at the same time With that much lift, it would be taxing to say the least on the nose of the rocker.
Next you said, "stock animal piston and connecting rod"...Which stock connecting rod? If it's a World Formula rod, maybe. Stock cast or even the L206 better rod will definitely not hold up to the kind of rpm that you'll want to turn with a P-Open cam.
Are you sticking with the stock PZ22 carb? If so, you don't even want to use that big of a cam. You really need a bigger carb (28mm) and big valves.
I guess what I'm trying to say is that "P-Open cam" and "stock parts" aren't a wise combination.