I'm running something very similar with great success...
I have 85 solid axle front discs and calipers on the rear axle. I got my brackets from 'Toywelder' on PBB. They mount more or less the same way as those.
While I was at it, I upgraded to vented land cruiser front rotors, with the large finned V6 4-runner calipers up front, also I'm running a 1988 supra dual diaphram booster and the supra 1" disc/disc master cyl.
Finished off with a summit adjustable prop valve.
I don't have any residual value, and have no problem with strong firm brakes on the first pump. Honestly the best brakes I've had on any wheeler.
I have maybe $250 into the setup total, which included new front calipers and rotors. The rear disc stuff itself is only about $100.
I'm stopping 38.5" SXs on home-made steel beadlocks, so about 550 lbs of rotating mass.
As tempting as it is to be cheap as possible, its a great time to get new pads, new hardware(those pins rust badly), new calipers if you can swing it, since those also tend to rust), turn the rotors, etc.
The bigger master and especially the bigger booster/master combo are the centerpiece for me. Gives me much more fluid volume, but the dual booster gives me lots of stopping pedal. The end result is a firm pedal, with reasonble pedal effort.