I can get a turbo case right now for $250 but it is a four hour (round trip) drive. Is it worth it to buy the turbo case now, and throw the shaft on the shelf for later when I do the duals?
If you put the 4.70 in the rear case you do not need a turbo case. If you put 4.70 in front you need the 10 spline input and 23 spline in the rear. If you are going 2.28 / 2.28 then get the turbo case. If you are putting the t-case on the back of the SM420 you need the 10 spline input and toss the 21 or 23 spline input.
Scott
