'68 Charger, power steering, firm feel steering box, but 21 years old.

Dead spot on-center is getting worse.

Obviously I'm going to look at the steering box, but is there anything else I should be looking at to eliminate the dead spot?

Thanks!

If dead spot means binds up in center. that usually means adjusted too tight.

What was caster set to at last alignment?

I had the same thing. Adjusting the box took most of it out.
Other things can contribute to the slop feeling. The bolts retaining the steering box could be loose. I've seen cracked brackets on the K member where the steering box is mounted.
The idler arm could be loose or going bad. The steering coupler may need to be rebuilt. There may be at least one bad tie rod end.

Thanks everybody.

Be sure to check the connection where the steering shaft enters the adapter on the steering box. I had the problem once, one of the little shoes in there was broke.