to be technical the extra weight may reduce some braking, but the added traction of a larger wider tire can also make up for it. The only problem I've had was once after making a panic stop on the freeway, the brakes became too hot and had a horrible fade for about 10 mins. If you have the money to spend, beef them up, otherwise you might wanna get used to glazed and warped rotors. Oh wait, the rotors warp easily with the stock setup, on rangers. In that case don't worry about the brakes. You'll be fine.
2003 Ranger FX4 level II. 3" BL, 33x12.50 GT Radial Mud Claws, Custom front and rear bumpers with winch hookups, custom flatbed, with hi-lift, and full size spare mount, 12,000 lb winch mounted under bed, Electric fan, and of course a flowmaster.