I had 31x10.5's on 15x7 rims with a 2+2 lift and very minor trimming. I also had 33x9.5's on the stock 5.5" rims with the same lift. I'm also of the the opinion that first you work out what size tyre you want to run and then figure out how to fit it with the least amount of lift. For the ride I'm putting together at the moment I've gone old school with some 7.50x16's (mainly because I already had them and some internal pneumatic beadlocks to suit) on 16x6.5 Sport rims and the Calmini 3" suspension. They just sit inside the wheel arch. I don't need a body lift and only need to fold back the seam in the rear of the front well and remove the mudflaps from the rear. The steering stops will need the smallest adjustement as they just touch the chassis on hard lock fully flexed. The great thing about this for me is that with the factory rims and small lift it doesn't attract unwanted attention from the law.
With your 15x7's try looking for something with a -10 to 13 offset. I think the stock 5.5" are a 25P offset (1" positive) or 4.25" backspace although you may have variations in the U.S.
The 2" bodylift is nice and easy where the 3" requires a bit more fiddling around.
Think about your gearing too. With a 16v and auto with 5.12 diffs and 31"s the gearing was bearable but the 5speed suffers more. 31's seem to about the average limit (30's are definately easier all around) without to many problems, bigger than that is where more things are starting to get stressed and gearing becomes an issue and more cutting my be required.
Really it's going to depend on the type of driving you intend doing with it and what you don't mind changing and spending as to the final configuration that suits your needs.
Got to say with some decent rubber, locked and some t-case gears these rigs amaze a lot of people. Have fun.
