I bought two minis a few years ago. A standard walmart model that had a nice wood stock, and a "tactical" model with the black plastic one. I swapped the stocks no problem. I haven't owned a pre-580 mini, so I couldn't tell you if the earlier furniture fits.
Wood stock on the Tac model is, imo, the best looking and shooting. Good luck!
"An angry prophet, denouncing the hypocrisies of our time"