Those are just foreign made copies of a BBK # 1515.
They are designed for standard plug angle heads. They will physically bolt up to a GT-40P head because the exhaust bolt pattern is the same (of course), but the revised spark plug angle will make installing and removing spark plugs a serious pain at best, and may be very close on certain plug boots.
You want Mac Headers # 50158 or Ford Racing M-9430-P50 or M-9430-P51. Those headers were designed specifically for P heads.
Those are just foreign made copies of a BBK # 1515.
They are designed for standard plug angle heads. They will physically bolt up to a GT-40P head because the exhaust bolt pattern is the same (of course), but the revised spark plug angle will make installing and removing spark plugs a serious pain at best, and may be very close on certain plug boots.
You want Mac Headers # 50158 or Ford Racing M-9430-P50 or M-9430-P51. Those headers were designed specifically for P heads.