All iron GT40 heads have the same size valves except the exhaust valve in the GT40P head.
GT40 = 1.84"/1.54" (intake/exhaust valve size)
GT40P = 1.84"/1.46"
non-GT40/P = 1.78"/1.46"
GT40 = 1.84"/1.54" (intake/exhaust valve size)
GT40P = 1.84"/1.46"
non-GT40/P = 1.78"/1.46"