I may have an opportunity to get a rear axle complete with e-locker, wiring, and switch from a wrecked '97 for a real good price. If I do, I will want to regear to 4.56 or 4.88 before I swap it, so then I can run 285's easily.

I also recently got a set of stock 265/70/16's to use for highway driving, since I wasn't really planning or expecting to get access to an axle/locker. If I decide to hang on to them, what would mileage look like? Usually people ae asking about running bigger tires on lower gear ratios, not the other way around.

 

Not that I know much about tires but I think if you do the tire calculator you're going to find that you'll be running more miles than actually traveling and prematurely aging your car with non-existant miles.