I'd use the gt40p's. The header issue only applies to certain headers. Some fit fine and some don't. I put together a Ranger with a set of those heads and I used a set of FMS headers for a 94-95 mustang, Had to use 90 degree plug wires, some heat boots, and I had to use a wrench on a few plugs to get them out. A chore to change plugs, but they worked fine. There are a lot of header choices with easy plug access but they were limited for the Ranger at the time. I made 290HP to the wheels with a unchipped back yard tuned EFI setup and an old technology B303 cam. The heads were bone stock except I polished out the rough casting in the ports and the chambers. The thing I really liked about them is I was able to run 10.02:1 static compression with never a sign of detonation. I even sprayed nitrous a time or two on 87 octane and no detonation. My guess is the combustion chamber design. I made 337 to the wheels with a small dry shot of N20 and the truck ran a traction limited 7.75 through the 8th mile. Not too bad for a set of Ford Explorer heads in my opinion. I think the P heads are the best production Ford heads available and the Mustang enthusiast sites back that up. If you don't have header issues I think the new technology will serve you best....My opinion