I have two Rust free trunk lids. How do you tell a supreme from an S or are they the same? I am currently working on a Cutlass S.

 

On a '68 & '69 two door, they are the same, however on a '70 etc. the Supreme lid will be about (55 1/4) three inches narrower or so than an 'S'... Similar to a convert but with square corners at the top.

 

So it looks like they are both cutlass s trunk lids One has small chrome trim the other has a Oldsmobile trim across the bottom above the bumper Are they year specific or just a trim option?

 

Depends on the year. 1968 and 69 are one-year-only. 1970-72 all interchange (again, assuming you have the correct one for your body style). The difference in chrome trim is unrelated - that's just a different trim level thing.