I added them to my '79 CJ5. I bought a used power brake booster/master cylinder from ebay. It worked better than the non power brakes that I had.
Then, I read a bunch of articles how a YJ power brake system was an upgrade over the CJ setup. So, I bought one of those, and swapped it in. I have GREAT brakes!! And, I don't even have the double diaphragm booster that was available in some '95 YJ's. That one is supposed to be the best.
Just install the booster/MC, and run the booster vacuum hose to a manifold vacuum port in your intake manifold (I have a V8 manifold). Bleed the brake system, and you should be all set.
I modified the booster pushrod (made it adjustable), because all the articles said to. I really don't think that it was necessary for me to do so.
Google "CJ to YJ power brake conversion." There are quite a few articles on it.
'79 CJ5, AMC 360, t-18/d20 twin stick, dana 30/amc20(Mosers), Edelbrock Performer intake, Holley 600, ps/pb, DUI HEI, 'glass tub/1pc. tilt nose, 33x12.50 BFG AT's.
There's a fine line between "hobby" and "mental illness".