You may find that the tie rods are more of the culprit than the steering box. Replace them first, then re-evaluate the steering response.

If I buy a car that I plan to keep for some time, I'll put it up on stands and strip it to the frame, replacing control arm bushings, ball joints, tie rods and ends, idler, pitman and steering box. It is such a pleasure to drive a car with a whole new front end under it, just like the day it was delivered from the factory.