You know how the world works today, these boxes are probably rebuilt by illiterates in some third world country. If not now, in the near future. I understand the risks and think I am up to the task. The costs of parts and tooling would be the downside to me.
What are the costs of parts and special tooling?

My steering box is ok but could be better. It is not worth it to me to buy a rebuild for the difference. If I could rebuild it for $50 or $80, I would consider.