On my Ranger, I'm running the stock master cylinder, works fantastic... I made a coupler for the parking brake cables, when you extract the axle from the junkyard grab the frame bracket for the parking brake cable on the axle end, mount that to the frame and adapt the ends together with something...
Oh, while you are at the junkyard, grab an extra passenger side brake hose from another Explorer, put that on the drivers side in place of it's T hose, get a Harbor Freight tubing flare kit and mount your stock rear brake hose to the Explorer axle and add the fittings from the old brake lines to make it work... it will allow for more suspension travel...