If you have a Shop Manual, check in the Steering section for adjustments (and, to determine the amount a wear in critical parts).
This is an important adjustment:
This 1955nd manual technique should be the same for you '56. (steps 4-6)
It made a large improvement for wandering in '54 Suburban.
You can buy a "Steering Gear Scale" at Walmart (a small/light fish weighing spring-scale).
Also, play with the tire pressure:
- too high - you will wander too much
- too low - steering is difficult
