Similar issue on my 70 Challenger RT after replacing steering box with another. Long tale of woe posted elsewhere on this forum. Could not get proper toe even with one tie rod end adjusted 3/4 inch longer than opposite side. Even this would not allow steering gear to position on top center.

Finally shimmed steering box mounting to K member. All is well now.

Does your steering shaft appear to go perfectly straight from firewall on engine side of it into steering box? If not, a shim to straighten it out could be your ticket.

The question then remains is why ok before, and not now. What changed, or was alignment always off a bit.