An alignment shop can't really do much for these solid axles besides adjusting the toe (which can be done yourself) or helping detect a bent housing. They would have to be Toyota SA specific and make or stock steel shims and have the ability to do a "cut and turn" to be worthwhile.
Here's a snippet from 4crawler site on checking your caster
"If running taller than stock tires, you may want to reduce the caster angle a bit. The reason being that the effect of caster angle is to give a horizontal separation between center of the tire's contact patch and the point where the ball joint or king pin axis would intersect the ground. The taller the tire, the less angle is needed to create that same separation.Here is a link to Toyota solid front axle steering alignment specifications. On the Toyota front axle, an angle of approx. 6° up (front of perch higher than the back) on the spring perch provides a decent caster angle (Note: this measurement is related to but not the actual caster angle). At this caster angle, the stock front pinion angle will be tipped up ~5° from horizontal (or 85° from vertical). So every degree you tip the pinion up/down will result in the same caster angle change. Too little caster will give poor return to center and wandering at speed. Too much caster will give a heavier feel to the steering. Best to shoot for a caster angle in the middle of the range. Realize that the caster angle will change as you change the rear ride height, either due to changing the suspension or adding load. This can be in the range of 2/3° - 1° per inch of ride height change."
