part # 51765
That is an incomplete part number. The full, correct part number number is 51765-S13, the -S13 being the Ford finish code. It is 10-24 X 1/2 inch long pan head screw (Phillips drive). The -S13 signifies a chrome plated finish. The screw you are concerned about has an incorrect finish. This screw was used on Mustangs from 1964 thru 1967. In 1968, Ford used a -S9 finish, bright zinc plated. AMK sells the correct size, but only has -S8 finish (zinc plated) available (and -S2, phosphate).
Jim