1-2 " t-case drop is plenty there . REad the How to on the gear swap . AS for a gear size 3:90 - 4:30 ratio would be about ideal for 35" tires and up . Also the carrier will dpend if it need tore down if u swap gears which u will cuz the ring gear has to come off of the carrier . AS well as the carrier bearings . All this will need done if u add locker for sure .