Are the P's worth the trouble of needing special headers over the regular GT-40s?  Also, from what I have read smaller chambers on the P's result in a bump in compression, it shouldn't be anywhere enough to put my stock pistons in danger, should it?  I believe my motor has cast pistons, but I'm not sure.....are they decent or would hypereutectic be better?  Also, what came is good for a carbed 5.0 that isn't crazy expensive.  Summit told me that Ford racing alphabet cams are for EFI and only pointed me to some $300+ Comp Cams one...