make sure the steering rack is centred before installing the input shaft spline pinch yoke and tie rods to the knuckles. The rack mount should never be changed or altered as it requires its correct angle to work smoothly.
If you dont have the steering returning back (centreing) itself then firstly check the ball joints for any slop or lack of grease, I have even seen mechanics install new ball joints and not fill grease into the joints. The returnability problem is a caster angle issue and extreme slop in ball joints. Check the caster angle and see what is damaged to cause the caster to go off.
to understand it - look at the front wheel of a motorcycle
the angle of the shock absorbers is the caster
as you turn the wheel the wheel slops over inwards into the turn - and forces the motorcycle straight as soon as the driver shifts body weight to straighten the bike.
cars are exactly like that except you have 2 working in unison. In adjustable cars, the caster is adjusted by a longitudnal setting, in your case, its chassis damage as the caster is fixed.