89 b2200 manual steering gearbox thread size

Hi,
I need help finding out what is the size of the thread on the shaft that holds the pitman arm in place I damaged the tip of the thread. I would like to know before I purchase an expensive die to fix the issue. Thanks ahead of time I really enjoy looking at everyone's truck on here for inspiration.

Can't you file the thread with a small triangular file, or grind away the damaged area and get the nut on?

I just pulled a B2200 power steering gear yesterday (don't know if that would be same size, on my workbench) but there were enough threads coming past the big nut that losing a few would not be a big deal.

One my new "used" power steering gearbox, the diameter is 20mm, and the thread pitch looks like 1.75mm. But manual might be different; big nut takes 27mm socket.

I am going to try it today. I will see if I could get a bolt to check the nut. Thanks