So, you think it'll look weird with the body lift and 31s? You thinking I should just go ahead and save the money for rims? That's not a bad idea actually.
Well if it were me thats what I would do. A body lift with all the proper stuff will be around 200 or like 250 if you have a manual transmission. Also on my 84 there was less stuff to get broken or interfered with (no A/C anymore, no extra wiring ect...) In your 99 ther are tons of wires, lines and ground straps that will need extended (all in the kit but its just a pain to do all that). And since your truck can fit 31's perfectly stock and it looks good, it will look goofy if you leave 31's and add all that extra room for 33's. Plus personally I love the extra room for tires but you can see the frame afterwards and that just doesn't look right.
If you did decide to go up to 33's you would most likely need to regear which would cost you even more money.
I would really recommend saving your money on the body lift if you plan on going with 31's, i think my 31's almost look too small with no lift but thats just me. Save your money and put it towards a nice set of rims with your tires is my advice. I got that set of Black steel rims for my truck for 300 bucks new.
If you want though, I would recommend cranking the torsen bar and leveling the truck, getting your tires and rims and then getting an alignment. some places will include a free or discounted alignment with the purchase of new tires.