Hi James,
A huge amount will depend on the choice/availability of the RS/AMP brake callipers for you. Thee AMP system was a completely different standard to ISO 2000 tabs and more modern post-mount systems, so front and rear bolt spacing, rotor size and rotor offset etc are all different to current norms.
If you can source a set of RS/AMP callipers, then you'll need the specific RS/AMP/White Industries hubs to match, with the 3-bolt rotor mount and 160/140mm RS/AMP rotors.
-Front hubs seem to turn up reasonably regularly on eBay. I have a silver 36 hole front AMP hub available.
-There is an original AMP hub adapter knocking around which certainly fits the gunmetal grey Shimano XTR 950 rear hubs. Not sure if it would work with a front hub.
-Brake-stuff.de do make new copies of the AMP rotors:
http://brake-stuff.de/produkt/41/Bremss ... kShox.html
If you go with fitting standard ISO or post mount callipers (which is probably going to be easiest), you'll need calliper mount adapters, but then you can use any standard QR 100/135mm hubs, and brakes.
I made a set of adapters, ran Hope Mono Mini Pros with 160/160mm rotors, no problem. In theory this will cause greater leverage on the rear stay than it was designed for, but I'm no monster rider, so I don't worry.
Cable operated or full hydraulic calliper makes no difference to fitting.
I haven't heard from B3 in a while, but you can find a lot of sketches and drawings for the adapters here:
http://www.retrobike.co.uk/forum/viewto ... p;t=108600
All the best,