I have a 71 fj40 and am swapping mini truck knuckles to get disc brakes, while I have the axle apart, I wanted to put marfeild or newfeild birfeilds in, but they only have them for the fine spline 75 and up . Has anybody done this before and have any solutions for me? Also should I change to 4:88 gears, while I have the axles apart? I'm going to run 39.5 swampers, and I'm running a 350 small block, sm465, and a toyota 3 speed transfer case. Thanks