A Dallas-built version of the P-51D designated the P-51K was equipped with an Aeroproducts propeller in place of the Hamilton Standard propeller as well as a larger differently configured canopy & other minor differences The photo reconnaissance versions of the P-51D & P-51K were designated F-6D & F-6K respectively The RAF assigned the name Mustang IV to the D model & Mustang IVA to K models Skill Level 3