As far as I know, all the front rotors are interchangeable.
Rear rotors are smaller and thicker, but take a similar brake pad, same shape, more meat on the pads, although I fitted a half worn set of fronts in my rear caliper in an emergency - work fine.(for the 89-92 models)
Please anyone knowing better correct me, but I think that's the case......
Have a look at www.mrcycles.com - check out the rotors for the different years..........

 

Cheers mate

 

Front rotors from '90 on are the same. I think the rears are smaller in the '93 and up but not sure. I know the wheels from '90 on are the same, front and rear. Maybe that will help.

 

Dad - that clarified it - cheers