GMC bumper guards during these years were standard equipment and stamped from the same heavy gauge metal as the bumper (a different style and lighter gauge metal were dealer accessories on Chevrolet light trucks).
A slight change in design was made at the end of the 1956 year. A more decorative pointed end was given the guards during 1957 through 1959.
1955-1959 GMC (above)
1955-1956 GMC (above)
1957 GMC (above)
1957-1959 GMC (above)
1955-1959 Chevrolet (above)