Yea, to run bigger tires, you have to get a lift and gears. Might as well throw a locker in while your switchen gears. You're right it's better to do around the same time and will cost some $$$. Marlin ARB V6 3rd is about 1300$. Detroit third is about $1000. You could get a junkyard third and buy the ARB and parts. Do you feel confident enough/or have skills to install the ARB yourself or find someone to do it? Which is cheaper. Depends on if you can get a deal on the ARB and junkyard third and if you do it yourself. If you got a third from marlin 4.88s, then you would have to get bigger tires and suspension lift (more $$$). I think it would be a waste of your time and money to put a locker in w/4.10 gears when you're probably going to want to replace soon anyways. Trust me you'll eventually want bigger tires, we all do!