Your wandering could be a number of things:
-worn tie rod ends or other ball joints
-did you roll the vehicle back and forth and check your toe-in again?
-Older bias ply tires can pull in strange ways, only replacing can tell for sure (or maybe just rotate front to back and see if anything changes)
-Your caster may be off, that has as much or more to do with straight line stability as toe-in. Hope that helps.

'69 1/2T stepside, Sea Foam Green, 250 L6 w/ 3 on the tree, not an option on it, in the family since new.