there are a few parts that you'll need, including a fitting to fit on the carb for the vacuum source, along with all of the hard lines leading back to the axle. fwiw, the original 2-speed equipped trucks also had a special speedometer that also had a vacuum fitting, so that it would still read correctly when shifting the axle. additionally, you'll need a shift button/pull cable to actuate the "shift", usually mounted on the gear selector tower. the cable runs to a diverter mounted on the firewall, which is plumbed into the piping between the carb and the axle. don't forget the vacuum diaphragm on the axle itself.