Welcome to KCZuks, Wormy!

An SPOA alone will give you enough lift for 31 inch tires. You can reuse the existing parts and get by for nothing, or buy a kit and spend as much as you want. Depends how much flex that you want. Just keep the lift to 6 inches max, or your drive-line angles will be too severe. Body lifts are inherently evil. You will have to get new wheels with less offset, or your tires will rub on the springs at full turn, where they could hang up and break an axle or something.
There are yahoos who will break anything, and there are those with the right touch who run amazingly huge tires with a mostly stock drive train. However, 31 seems to be about the limit for a drive-train that you can beat up confidently with a mostly stock drive train. I say "mostly" because to run the larger tires with a straight face, you need to gear things down in the transfer-case and/or the differentals. With stock gears and big tires, it's like starting in second; you can't go slow enough to crawl, and you don't have enough power to use fifth gear. I'm very happy with my 4.9 t-case and 31s. I would not want to go any slower in low, and my high ratios are close to stock. Don't be sucked in by gears that are too low. You might have to back up in the mud!