I am almost positive that 1st Gen 4-door S Blazer has the same seat belt / retractors as Syclone. (I used to know for sure, but it has been a long time, and I no longer own a 4-door to take a look at to confirm.)
There are a couple of different height buckle ends. Again, IIRC the pick-ups have the taller / longer inner buckle, and the utilities have the shorter.
Black is another hurdle as 4-doors predominantly had tan and gray interiors.
Not much help, but another possibility.