I don't have used OEM Clutch Pedals at this time, so I will use Corvette Central Reproduction Pedals to show differences and the evolution of Vette Pedals.

This pedal has the upper push rod bracket spot welded on with a 5/16" clearance hole for the push rod in front of the pedal "beam". It has an approximately 1 5/8" x 3 1/4" pedal pad.

This pedal is identical to the 56-57 except for the pedal pad, which measures approximately 2 3/8" x 3 1/4".

*The Chevrolet Parts book lists this as a 55-58 part, but there are obvious differences in the pedal pad. My guess is you would get the 1958 pedal, then you would have two different pedal pads.

This pedal is identical to the 58 except with no push rod bracket and two 11/16" thru holes in the "beam" for the upper push rod bracket attachment.

The 1963 model year had a radical change in their shape, with a large off set bend and new pad shape. The two (2) 3/8" clearance holes are for push rod bracket attachment, as there are different brackets for small block and big block engines.

The 1967 pedal has the same shape as the 63-66 models with a welded on push rod bracket.

1968 saw another major change in shape and design along with the Corvette exterior. The offset is much less and there is a pin for push rod attachment.

The 1980-1981 pedal is identical to the 1979 except for the smaller trapezoid shaped pad.

Disclaimer:
 
Factory correct applications are your responsibility. GM made part and part # changes with no rhyme but a reason (no production interruptions at any cost).
Application charts and part numbers are for replacement parts that were available at the time of parts book printing.
My observations come from the parts I have in my collection or other reliable sources your parts may differ.
If Factory correctness is your goal, do more research, join car clubs,
 forums and buy an assembly manual if one is available for your Project Car (you wont be sorry).
This is a fun and interesting part of the hobby!