Something else to check, in addition to the steering box adjustment Jerry mentions, is the preload on the tie rods if you are still running the original style. If the preload isn't right, that can also cause problems.
The adjustment is quite easy, though you will need to get a drag link socket (I forget the size) which basically looks like a large slotted style screwdriver. To adjust the preload, you need to remove the cotter pin from the tie rod housing. Then the end plug needs to be tightened until it can't be turned in any further, which means the spring is fully compressed. The plug is then turned back to the first cotter pin hole, and a new cotter pin is installed. This needs to be done on both sides, and the toe will need to be rechecked afterwards.
