The adjustment procedures should be in the 1963 chevy manual. I also would recommend checking the drag link which is the rod with a tie rod end on each end that connects the pitman arm to the steering arm on the axle. If it is the original most likely it is shot as it takes the most punishment driving over ruff roads. The way to check it is to have someone turn the steering wheel back and forth while you watch each end and you will see if the rod is moveing with out the ballstud. You must leave the tires on the ground for this so there is resistance. Also dont turn the steering wheel very far in each direction. Just a 1/8 to a 1/4 of a turn each way. You will feel when the slop changes over to steering input and you dont want to turn the tires you just want to tag each end of the slop sone. Unfortunatly I havent found anywhere that sells a replacement draglink yet but I think with a little trial and error a person could built an adjustable one with two tierod ends and a sleeve, you just have to find tierod ends with the right diameter and taper to fit the steering arm and pitman arm. Good luck with your project as these are very cool trucks.
