How did caster get into it?
Never mind.
There are corrected radius arms that may or may not do much for the axle's caster angle, but relieve the stress from the frame-end bushings by having a bend in the arm (typically, gusseted and welded) when the taller-than-stock springs are used.
There are caster-correcting arms that may or may not do much for the bushing, but rotate the axle backwards to regain the proper caster angle. The flip side of it is that they also rotate the front axle pinion further away from the transfer case yoke, forcing you to use DC-jointed front driveshaft.
In either case, whenever the front axle is further away from the frame, the axle is shifted towards the left side of the truck. It isn't that large of a shift for 2-3" of lift, but enough to get your steering wheel cocked to the side - which people (like me) compensate for by adjusting the length of the drag link. As a result, the steering box is off center when the truck moves in a straight line - and being a progressive-rate box, it only can have no play in the dead center.
Using an adjustable-length panhard rod allows you to keep the steering box in the centered position.