I am going to swap out the factory rear axle assembly in my 83 Cutlass to one that came out of a Cutlass that has 373 gears and an 8.5" rear end. The new assembly is drum to drum complete. Before I install it, should I do anything about the internals of the differential while its out and readily accessible? Such as a rebuild kit or something similar? Never done a rear end swap so any and all help is appreciated. Thanks!