The main differences are the barrel (as mentioned above), and the sights.
Any Mini-30 action will fit in any Mini-30 stock. If you get a Mini-14 stock, you will have to remove a bit of material from the magazine well in the stock for a proper fit.
, all aftermarket stocks are designed to fit the Mini-30 or -14, so there should be no need to do any fitting if you go that route.
Also, all ventilated handguards will fit any series of Mini, regardless of caliber.
Can you change this?