Did I really mess this up? Rough alignment issues (uneven tie rod length) after steering box and spindle replacement

First, thank you for the detailed explanation! Really makes it easier to follow what’s going on. Now, to confirm a few things

-the pitman arm has master splines that only allow 4 possible positions on the steering box (only one of which can be correct for this application)

-the steering coupler has no master splines at all

If that’s all true, the issue is almost certainly that the steering shaft/coupler are not quite center of travel for the steering box. Could be for a lot of reasons but keep in mind that your steering stops, or even the suspension points of the car, may not be perfectly equal side to side. So equal turns on the steering wheel might not be the middle.

what I would do is

1- separate the coupler from the steering box

2- make the tie rods equal length, setting so your wheels are straight ahead. Don’t even worry about the toe in, because it’s gonna be the same side to side and it’s easier to verify the wheels are straight ahead.

3- verify that the steering box is relatively close to middle of range, and proceed if it is

4- put the wheels back to straight ahead, and make the steering wheel straight when you hook up the coupler.

The wildcard in this is #3. If the steering box isn’t in the middle when the tie rods are equal length, you’ve got to figure out why.

Again, my understanding of the Borgeson box is that the pitman only goes on 1 way because 90° off is massive. So if you can’t change the pitman on the box, and the box isn’t centered with the tie rods equal (completely ignoring the steering wheel), the your steering stops aren’t symmetrical. Which means go back to step #2, put the steering box in the middle of it’s travel and your tie rods won’t be equal.

The steering box is right, but the car may not be symmetrical. Remember suspension points on these cars have significant tolerances.