A six cylinder will not fit in a '57 that originally had a V8. The radiator is mounted further aft on a V8 truck. The radiator support is attached to the frame. The location of the brackets on the frame is different on V8 and 6 trucks.
A new radiator support may be located in the 6 position but the original support will have to be cut and the mounts still bolted to the V8 brackets because this is what holds the front sheet metal to the frame.
Also changing emblems will not make your truck "original". Original is how it came from the factory. When any parts are replaced it is no longer original. It is highly doubtful your truck still has the original tires, brakes, shocks, etc.
