Adding a lift kit won't do anything for more ground clearance for the axles and diffs., but it will help alot to improve your breakover angle, which I've found to be alot more a problem than any 1-3 inch increase in ground clearance will help.
Yes, one needs to understand that going to larger tires can easily add more to alot more stress on the key components of the truck. It can also depress the vehicle's ability to pull at low speeds when off road. Not good when you are trying to climb a steep grade on a chewed up road. So, if you are buying a new truck, you want to plan ahead and order axle ratios in the 4's if possible.
As a rule, adding only 2-2.5 inches of lift usually doesn't require many modifiactions on other components. But each vehicle is different. What I'd do is talk to those who do such things for a living and do a complete package when lifting an off road vehicle. E
