As far as I'm aware no Rocky's were fitted with Limited Slip Diffs (assum this is what you meant) on the UK market at least. Is it a UK wagon? You call it a Rocky, so is it an import.
Anyway. Easy way to tell. Jack the rear axle up so both rear wheels are off the floor. Leave it in gear (so the prop wont move. Now spin one rear wheel by hand. If the opposit wheel spines in the same dirrection, its a Limited Slip. If the opposit wheel spins in the opposite direction, it's a standard diff. And if it wont turn at all, you've left the hand break on.

Any veiws expresed in this thread by me are purely from my own experience, and (sometimes) falible memory. Hope my comments help, but please don't take them as gospel.