I take it you have a 4.0 since you don't already have 4.10s. I personally have 3.73s and 33X12.5 but also have the six speed. It does well enough for me but 4.10s would be a fairly safe bet as well. If you don't know someone who does gears that you can really trust to do them right be prepared to spend about 600-1200 in labor alone. May be cheaper to pull the axles and drop them off.