You might hunt down a sector gear ( pitman shaft ) and see if that will help tighten up the steering. If the worm gear is OK and the bearing races are OK, then you should be able to make it all work. The ball nut can wear in the straight ahead position, but a new sector gear may be enough to compensate. Bushings can be sourced local from any bearing retailer, bearings can be had at most venders in the above links, gaskets you make yourself.
Check e-bay for sector gears, I see every now and then.
