basically, for a BDMT, think big tires and high wheelspeed...that means a good BDMT has plenty of torque to get the tires spinning, and lots of horsepower to keep them spinning at a high speed. It would also need some hefty axles to handle the weight of the tires and the pure abuse that causes.
now, if your looking to play in the mud with this Ranger, and do it on the cheap, then just take a sawzall to the front fenders, ditch the bed, move the rear axle as far foward as possible, stick the biggest tires on it you can, and have fun
the best way to build a BDMT is to start with a 3/4 or 1 ton truck, preferably the older trucks, with a solid front axle. Then you already have the V8 and decent axles, lift it and add some tires.