Both caps have a large S in the middle.
The original cap has a "sm" logo on one ear - the replacement just has a 'S" on the ear.
That was the only difference I saw. The replacement cap is still available from GM.
You guys are right....
Went back and compared.
The replacement caps are not even close to the originals.
The original is round with raised letters, and an sm on the grip.
The replacement has ears, Stamped letters, with only a S on the grip.
The big "S" is the only similar trait.
The replacement does look like it would work better.
Been a while since I looked.