ok im gunna be installing gt40p heads on my mustang soon ,the heads looked to be rebuilt at one time but dont know for sure, i want to just stick a cam in with the heads and not have to change springs,pushrods, etc. cam i do that with stock p heads or do i have to replace stuff, any cams that are safe for the stock springs that i can get away with? thinking of a trickflow 1 cam or ford b-303 or e 303 cam for now.