A certain amount of bump-steer is inherent in the design and affects modern heavy trucks with straight axles too. The longer the drag link the less the bump steer. Changing the wheel offset to the outboard side will radically worsen bump steer as will wider tires on wider rims with the same offset. I was taught never to wrap my hand around the steering wheel with my thumb to the inside. Especially on rough ground the steering wheel can spin and a spoke can dislocate your thumb when one front wheel drops into a hole or such.
Front end alignment is part art and part science. In one of the better truck shops I worked in, the Bee Line rep came around with a half-day lesson on alignment. Two things have stuck with me: Engine torque will twist the frame and load one wheel more than the other and change the camber mostly on the passenger side. Not an issue with a 216 but certainly will if one stuffs a big block in an AD truck. Watch a long-wheelbase semi pulling a steep grade. You'll see the front bumper is way off level. When the driver shifts gears the cab and whole front end of the truck will untwist several inches when he throws out the clutch.
Second, crowned roads will need to be compensated for or the bias-ply, passenger-side tire will wear on the inside. Also caster should not be equal side to side to avoid pulling to the downhill side of the road crown. That leads to tired drivers and complaints to the shop. On a dead-level road it should pull slightly to the left. On trucks with dedicated drivers they'll tell you what they want if you ask. They know what routes they run. Also sagging springs will affect caster and handling, as will tire size and pressure. The latter two affect "trail" and make steering lighter of heavier with no change in caster angle. The list goes on. Any change from stock configurations will negatively affect handling, except on Jerry's circle-track cars.
Read Jerry's method of toe adjustment carefully. It makes a big difference. Few alignment shops will load the tie-rods when setting toe-in, even when the spec sheets requires it and I ask. Like on my 84 Mercedes. Make sure the springs in the adjustable tie-rod ends are under enough tension, likewise the drag link. If the springs are soft, toe-in will change on turns, especially at higher road speed.
On trucks that run on the interstate there is a different set of variables to take into account. And radial tires are aligned differently from bias ply tires.
I would interpret driver complaints of "shimmy" on a truck with 20" wheels to be worn parts, not balance. Balance will produce a "thump" with each wheel rotation. At 60 MPH it'll be about 550 RPM or about 9 cycles per second for an 8.25 X 20 tire. Maybe that could be called a shimmy, it's subjective. I'd ask the driver.
