you want a 44 from 77 down withe the weld on wedges not 79 with cast c's tnt makes real nice truss that is what i run. the nine with 31spline and yukon chromoly is plenty i run 38.5 tsl/sx and have no problems nodular with 4.88 and detroit explorer disc brakes
i have a 231 in my xj. i cracked the cases when i broke front drive shaft. i dont have another 231 handy but i have access to a 249 out of a grand do they use the same cases. my internals in my 231 are good and would like to just use the 249 cases i have a teraflex sye so dont need anything else...