When I did the swap into my '61 Apache, I removed the original 3 speed(Muncie) and replaced with the OD. Exact same length, bolts up same way, same spline count on input and output. No driveshaft mods necessary. Plug 'n play as they say:) If you are using a later Saginaw type unit, I believe the spline count on the output is different, you'll need a different yoke.
