First and foremost, have someone rotate the steering wheel back and forth while you lay under the front of the car and look for any looseness in the tie rods and ball joints - if those have any looseness rebuilding the steering box won't help.
Then, look at the pitman arm shaft that goes into the steering box. It should not move forward or backward at all! If it does, the bushings inside the steering box should be replaced. Some times adjusting the slotted threaded stud (6.822) (illustration at
http://chevy.oldcarmanualproject.com/parts/1929_54/397.htm) on the outside of the steering box will take up some slack. Also try adjusting the 6.532 adjuster will help (it limits the up and down slack of the steering wheel). The steering idler third arm (6.179) in this illustration (
http://chevy.oldcarmanualproject.com/parts/1929_54/378.htm) is frequently the culprit.The pin and bushings where this assembly is bolted to the front axle are a frequent wear point and the cause is lack of grease. Check also for worn king pins.There is a reason Chevrolet specified that all these points (except the steering box) be greased every 1,000 miles!
My grandmother had my car serviced every month even though she only averaged 200 miles a month, never mind 1,000 miles! It was in great shape and I drove it 1,200 miles to Denver when she gave it to me when it was 21 years old and had about 50,000 miles. I then drove it as my daily driver for 6 years and about 200,000 miles, and I did not service it every month, so I know all about wear in the steering system!
