With the introduction of the new small block V-8′s in 1955 Chevrolet trucks, modified sheet metal was created to help in cooling. The new truck design came standard with the proven 235 inline six cylinder but when an optional V-8 was added, cooling modifications were necessary.
The short length V-8′s cooling fan was too far from the radiator and could pull air from above and below the engine and less through the core. To prevent this, all V-8 trucks came with an upper and lower metal baffle plate to help better pull air through the radiator.
These metal plates have become very difficult to locate in recent years. The lack of these two plates on (restored?) V-8 trucks are usually a strong indication the vehicle has been converted from an original six cylinder. The mechanic was either not aware these plates existed or had no idea of where to locate them.
During 1958-1959 the shroud was redesigned. It became a more traditional metal circle as is found on more modern vehicles. This allowed even more air to be pulled through the radiator core.
The following photos show original Chevrolet radiator cooling sheet metal from 1955-1957 V-8 trucks. The dark lines on the drawing relates to how these plates fit in the original vehicle.