Hey Strick!
I think the metal vent frames were only installed on the forward vents. I have never seen a SC with the vents on the aft... I think any tin knocker/welder could manufacture them easily. My pair need some sanding and a powder job. (9) years ago I Awlgrip'd 'em - I got my $'s worth - just a little oxidation here and there.
If you need the dimensions, I could either mail you one of mine, or I could try to measure it up to STRICK't specifications
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But, as you mention, the recessed is nice if it were not too recessed....