did you 1st centre the steering box with a drill bit as described in the FSM ?
did you then measure the draglink to 495.3mm ?
did you then set each tie-rod to 300mm ?
(roughly check toe with a builders tape, should be very close)
once all that is done, only then can the steering wheel be replaced upon its splines
If the steering box has been taken completely apart in the past, and not re-assembled accurately, the above procedure will not work.
I will say its fiddly to get right…the Pitman Arm should point directly to the rear before steering wheels goes back on, or it will not be correct
The indicator assembly comes of as a unit, which is collared around the steering column, and is possibly adjustable
never let an alignment shop near a 420G, until they have assured you they will use the FSM, the page printed out by you…they use the steering wheel to set everything!