Early Klein Mountain Bike - need suggested component rebuild ideas
I think you're going to have to pore over photos and Klein fan-sites like oldklein.com to find the specs, answering one question at a time. 

In terms of the BB, I believe they were press-fit bearings, in press-fit cups (like an old BMX), so you might have to remove them, measure them, and then approach an engineering supplies shop for replacements. Bearings are surprisingly universal so don't be put-off too easily by people saying "ah they are proprietary Klein bearings, forged by Klein faeries from Klein precious metals".. they are probably available!

The rear hub width can be measured easily by you, it's probably 135mm but that's a guess. Things like cranks will be square taper LX types, maybe something oddly 90's like bio-pace oval rings :)

I can't guess the model, but I don't remember the Pulse or Attitude havign internal top cable routing like that, so is it an Adroit? If so, I'm pretty sure they aren't the original forks.

Let us know how you get on! Lovely bike, I lusted after Kleins when I was 15!