The seatbacks can be modified for the belt to slip thru, but you'll need the trim piece for the front, and the bezel for the rear to make it look nice. Or you can swap the seatbacks....
On coupes, there will be a threaded boss on the side pillars for the upper belt slide, under the quarter trim piece. Convertibles of course will not have this...the pass-thru on the seatback is all there is to hold the belt up, afaik.
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Joel Adams
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"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"