# What Crayford focuser to buy for a B&L Criterion 8000?

I'd like to get a dual-speed Crayford focuser for my newly acquired a B&L criterion 8000 (8") as the mirror shift is pretty bad.

I'm really not sure which one to buy because I'm quite confused about the dimensions and potential adapters I need, and don't know how standard this config is. Let's call [A] the 4 screws-piece at the output of the optical tube, and [B] the threaded adapter that I'm holding in my hand in the 3rd picture. The ruler is in inches.

My questions:

• a) where would a Crayford Focuser like this one go? (edited after feedback) Should it replace part [A] or part [B]?
• b) what is part [B] officially called? and what diameter is it referred to by? (I measured 1.9in but can't seem to find anything like that on the Internet)
• c) how standard is this mount? Should I worry about the dimensions for what might replace Part [B]?
• d) can anyone comment with potential focusers that you think would fit this build? I'm looking for dual speed and < \$150

Thanks!

Note that I am aware these aren't the best scopes ever made but I do wish to keep it for a while.