go to MPH's site modularpowerhouse.com and check out what they have or search on this site and see what you come up with because there are many on the boards with P&P heads.
mostly people buy a set of already done heads and then swap them
Gains from PP heads depends on what other mods you have done to the car. If your stock exept for the PP heads you won't see too much of a gain but once you start running cams you'll notice a decent increase in HP.