you'll just have to look at the thickness of the clutch wearing material and the wear on the pressure plate fingers. If it is like new you should be good. are you certain the clutches are different between 79 and 83? if so it is surprising.

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.