I have fitted 1996 Discovery 1 diffs front and back to my 1969 Series IIA SWB Land Rover. The disc brakes are awesome. It turned out to be a lot of work but it can be done and is well worth the safety issue improvement
Cost of the diffs from a recyclers yard is+/- $500-00. The parts from Rovers North = 4 rotors, 2 front calipers, 2 back calipers, Brake pad kit front and back, wheel bearings, grease and all the diff seals, new drive shaft yoke for the back diff(eliminate the rubber dounut), 16 bolts for driveshafts, 4 u-jays, new mud splash guards, 20 new lug nuts, gasket maker, 4 spray cans of black paint. Front and back parabolic springs, 8X3''Dia spring perches, some 1"X3" mild steel flat bar. Also 4 Tie-rod ends. 1 Ton LR pickup shackles for the front.
Now tally up this part list plus add professional mig welding. I got this done for the whole job lot at +/-$180-00. The added bonus is the Disco side shafts don't break/shear off like the Series side shafts. Also the brake pades are off the shelf items. I have take lots of photos of the instal. Done some playing in the Pine Barrons of NJ. Now I need some ARB air lockers to really have an awesome Landy