I have 285/75/16 as well on my stock 2000 XLT 4x4.
The 4x4s do come with the stock 1" body lift, too, from what I understand.
FYI, 285/75/16 = 33" and 315/75/16 = 35" APPROXIMATELY
So, it is a decently taller/wider tire.
Once you are looking at 35"s and up, you might be wanting to regear the differentials, too. Just another thing to consider.
What the lift is going to help you with the most (I believe) is articulation. Then, approach/departure angles, then ground clearance, and finally fitting bigger tires.
Just my two cents. Hope it helps.