'85 will have front discs on the Dana 30, and rear drums on the AMC model 20.
This brake set up, when in good working order, will be fine for a stock rig, and should be fine for tire sizes up to 33". It will be a good idea to run light, alloy wheels to minimize weight if you run 33x12.50 tires.
You can drill the rear drums to improve wet and dry performance. Drilled drums are as effective as stock discs and better in certain circumstances. Personally, I'd take this approach over adding rear discs if you are staying at 33" or smaller.
(I ran drilled 11" drums on all corners of my '71 and it worked superbly, with 33s on steel wheels)
Look up C.H Topping for more info on drilled drums.
You can upgrade the rear brakes to disc but I have seldom heard much good about kits on the market to do this, such as SSBC