Grim covered it, but I will only add that while a 33x9.50 or 33x10.50 tire will fit on stock rims with no lift, don't plan on fitting chains in there if want to keep the fenders intact. If I can get a couple of hours I have a set of ball joint spacers to install and I'm hoping that the extra inch or so of space gains me some breathing room to keep from taking my fender lips off with chains.
Otherwise, doing the body and drivetrain lift, that is a ton of cheap clearance just waiting on a 4Runner. Although the drivetrain and fuel tank lift is easier on a leaf sprung 4Runner (up to 1989), I think it can be done on the second generations without too much trouble. But getting the gas tank moved up seems like a really good idea on your truck.
OME's kit is going to give you more like 1.5~2" of lift, there's only so much lift you can get from the front end without adding brackets. But with OME (or someone else) torsion and lower profile upper bump stops you can easily get about 1.5" of lift and still have just a little down travel. I think the true cheap way to lift the back is Land Cruiser coils. The stock 80 series ones I think give a 4Runner a couple of inches of lift and when they lift them they will probably give them to you, certainly shouldn't be much more than a case of beer.
I would avoid a 4.5" lift, no need for it unless you are doing 35" or 37" tires. If you are going to that height, just do the solid axle swap. Otherwise, stick within the factory parameters, add an IFS brace, slightly larger torsion bars and good shocks. Run a 33x9.50 or x10.50 AT and your truck will be fine. Then focus on sliders, bumpers, lockers.
Grim is right on about the idler arm. After hobbling a couple of stock ones along, I just dropped the money on a Total Chaos arm. But there are guys making replacement brass bushings for the stock arm and that would be an improvement. The stock ones with the nylon bushing last about one 'wheeling trip.
BTW, which engine do you have? I'm having trouble finding a snorkel for our body style trucks with a 22R-E. If you have a V6 or carb'd 22R, Safari's got you covered, just doesn't seem to be any love for the 22R-E ones. But then again I haven't looked too hard since a Safari is about $400.
Good luck and have fun!
