I just took some measurements, and it appears that the disk brakes on the back of the 200SX bolt-on to the H150 diff from the B210. The 200SX has an H165 or H190 (not sure which) so the axle is different. The bearing and retainer are identical to the H150, and the bolt pattern appears to match. This could be a bolt-on conversion. Anyone tried it?

One remaining problem is the master cylinder, need a much larger one for these big bore calipers.

Sad to say ...The 200sx axles wont work with the B210 H150 diff. The splines are different.
I had the 200sx rear housing and axles cut to the dimensions of the B210 differential to fit in my car. Besides why would you do all that work in putting disk brakes on an extremely weak differential that tears up the spider gears if you pop the clutch above 4000 r.p.m. with sticky tires!

later h145s, h150s h165s and h190s all that the same ends on the diff....so all have the same size bearings and same disk/drum mounting flange

and its not like its alot of work, all you really have to do is change the wheel bearing and when doing that put the disk stuff on instead of putting the drum backing plate back on

What handbrake set up do they use?

The handbrake cable is different, ill post a pic when I get home. A simple bracket mounted to the diff housing will work.

I think im going to grab the whole rear out of the 200SX and see what I see when i hang it under the sedan.