Thanks everyone for your thoughts and suggestions.

A related questions:
Does anyone have experience buying these steering boxes "refurbished"? I saw a couple of companies selling them for ~$400...800 and claiming that everything was rebuilt to specs.

Here is one example: https://www.buyautoparts.com/buynow/1984/Mercedes-Benz/300D/Power_Steering_Gear_Box/82-00116_R

I can hardly imagine how they could restore the worn mesh without putting in new parts.