I'm quite satisfied with the ride on my 87 however how would I know if I've still got the original shocks?

 

lean down and look at the back shocks from under the car, what color are they? that can tell you what kind you have yellow=koni's, green=bilstiens black=boge
as far as telling if they have ever been replaced not really sure, i would guess taking them out and looking for some markings