The bellhousing, clutch, etc. will be a direct bolt-in swap. You'll need to come up with the electrical system to make the OD operate properly and a shifter of some type, since the Saginaw was intended to be used with a column shift. Hurst used to make a floor shift conversion for that transmission, but you'll probably end up with some problems with shift rod clearance around the OD unit. BTW, a Saginaw with OD is a VERY scarce item and most people who know what they have will be asking an outrageous price. Another, less expensive approach would be to use a T-5 OD 5 speed in place of the SM-420. It's a weak sister compared to the 420, but it will give you better road speed. You'll lose most of the load-hauling capability of the truck, however.
Jerry
