The 1977 Datsun 620 pickup came standard with only rear drum brakes. Front disc brakes were not available until the 1980 model year. Some later Datsun pickup models, such as the 1980-1985 Datsun 720 pickup and the 1986-1997 Nissan Hardbody pickup, did come with front disc brakes. However, these front disc brake systems are different from the front disc brake system that was used on the 1980-1985 Datsun 620 pickup.
Therefore, the front disc brakes from a later Datsun pickup model will not fit on a 1977 Datsun 620 pickup without modifications.
