No doubt you can push those heads hard. I just wouldn't recommend them to anyone who is starting with a 351 block. If your plan is a 302 top end, don't spend money on a 351 bottom end. You represent a dangerous element on the internet. People see something on the internet, and instantly think they can replicate it. For every one person that runs a 12 on P heads, there are 50 who are stuck in the 13s, and another 150 stuck in the 14s; all wondering how you did it.
Kurt
I can attest to that! my car ran a 14.2 @98 with p heads and zero traction. really thought i could see a 13.x timeslip..that being said, these P heads aren't a factory unmolested set...they got big valves put into them and are ported, Im not sure if i can get into the 11s with even the best set of P heads. I really do like the 11r trick flows but GOD they are spendy.