Other things to lookfor--worn shackle bushings,a leaf spring "eye" up front that has opened up,allowing the bushing to slop around in it,and sheared spring center bolts,loose steering box bolts, or cracked frame rail where it mounts,can all cause it to wander....sometimes the REAR axle gets thrown out of alignment when a center bolt shears,or it has a sagging ,bent or broken rear spring too..Having any slop in the steering "rag joint" can make it difficult to stay on a straight course also..