As for the rice adaptors, that is mainly for clearence of the larger diameter tires. The RWA " ratio" is self determined by the unit. When you install a RWA, you just TEE into the supply line, that go from the Hydro pump, to the Drive motor. Then the oil just self equalizes between the front, and rear drive units( It travels the path of least resistance. Which ever circuit ( front or rear ) that has the least resistance, that is where the oil goes) They do make different size drive units for the RWA. This is to give more torque to the rear wheels for the larger size tires. Just start calling salvage yards for the units.and if possible get the largest unit you can. ( You can check Mud Hog Website, and that has some information on the different size units) Also a unit from a different make of machine will work on yours.The differance between them is the axle mountings,( if you are handy you can modify your axles so as the wheel drive units can bolt to yours),the hoses( due to where you tap into the drive lines) and the taps themselves (but most will work on any model). oh and also the color of paint. Try the salvage yards around Seikston Mo. a few years ago there were 3 large yards, and each one had quite a few units.HTH Joe