The stock diff is riveted to the final drive/ring gear, the MFactory comes as the diff itself without the ring gear. If your stock final drive/ring gear is not damaged you can drill out the rivets on the stock LSD and with ARP bolts you can bolt the MFactory to your old ring gear. If it is damaged you can buy a new one from MFactory or find a used OEM gear, I know MFactory sells different gear ratios than stock for the final drive (stock is 4.10:1) but they may have the stock ratio as well. Some people think the rivets on the stock LSD are what cause it to flex and shear the housing off.