From what you said if I got it right, when steering wheel is centered, so is the steering box, same turns ish, lock to lock both ways. But when the wheels are straight, the steering wheel (and steering box) isn't centered.
That's good, means the steering wheel is clocked right with the steering box
The right way, is center up the steering wheel (and steering gear), then use the drag link to adjust the wheels back straight (wheels off the ground). Remember tie rod only adjusts total toe on your type of truck, so I'd get the toe centered first it you haven't and still need to do that. Otherwise it's like someone with a lazy eye, you never really know which way they're looking!
Since your steering wheel and gear are clocked right, you should be well within the adjustment limits of the drag link to get the wheels straight.
Once all that is close, if the steering wheel is off a smidge, I just take it out of the drag link again, assuming I'll still get 98-99% full turn even in the short direction.