gpz 83 vs 84 shock. Interchangable?

I'm looking to buy a replacement for my 83 gpz 550 and have found a good deal on a used 84 shock off a gpz 550. But i'm unsure if those two model years have interchangable shocks. ANyone out there know?

not interchangable. you need 82 or 83. 84-85 is a totaly diff system.

Thanks a million, out of curiosity is the '81 compatable with the 83? I can't recall if it even had a mono shock at all.