I went from 342s to 373s. I am running 275/60/15 tires, on the OE 15 inch rims, on a 2WD. since it looks like you have bigger tires, I agree with the above. Go with 410s. Change all of your bearings, and I did the crush sleeve eliminator kit. Once you set the pinion depth, your done. It can not change. I was very glad I used it, when my pinion seal was leaking. It made it easy to pull off the yoke, and replace the seal, with no worries about changing the pinion depth. I also installed an Eaton truetrac to replace the OE open diff carrier. If you don't have a G80, you may want to look at a locker. The Eaton, is good on the street, but there are better choices for off road use.