High mileage on the 4.0L isn’t something we would be terribly afraid of. So long as the engine has been taken care of, there is no reason you shouldn’t be able to easily squeeze 250,000 (or more) miles out of it. Beyond looking for leaks, listen for excessive knocking or loud valve chatter. If the engine sounds rough but the price is right, it might be worth going for. There are a plenty 4.0Ls in wrecking yards.