On the stock AE type diff if you want a bearing on the inside of the diff hub close to the spur you will need to either machine it to accept a 1/4 X 3/8 flanged or buy an optional hub that has the pocket already machined in. If you want to have a bearing in the center hole of the spur again you will have to machine the part off the hub on the axle or buy another axle that accepts the bearing.