swapping one chunk for another? You only need a gasket w cement(my preference), several qts of the appropriate gear oil, a small bottle of the sure grip additive, Check & see if the flanges take the same size u joint, get the pumpkin seated all the way into the housing,only pull the axles out far enough for the pumpkin to come forward, adj end play when you're done. & last but not least give me 1st dibs on the 3.91