Might not be the answer you're looking for, but here goes:
I'm guessing here, so tell me if I'm wrong. You've got the drop-bracket style ifs lift and probably some spacer or coil to lift the rear. The ifs lift allowed you to fit 33s or 35s with trimming. You're wondering if you ball joint spacer the front, and get taller rear coils, if you could fit the next tire size presumeably 35-38?
If that's the case, then yes it would probably work. Here's a link to a 4runner site with the rear setup you're talking about.
http://www4.ncsu.edu/~jmgobien/html/4link.htmlThe rear coil lift is high enough, that you have to lengthen the linkages to the axle to get it to sit right in the wheel well.
However, I wouldn't recomend the ifs ball joint spacer lift with the tires you'd be wanting to run. The ifs axles are already prone to failure, but the spacers put the ifs axles near their lower droop limit, worsening the problem. Unless you plan on just cruising around town in your rig, the larger tires that would be used would certainly result in some sort of cv axle failure off road (likely when you needed them most: big mud hole, gnarly rock obstacle).
Most folks seem to go to the solid axle by this stage for the added strength, and the lift is easy enough after that, and the rear 4link coils are a nice addition. If you are set on getting the bigger meats, you might consider just some fender trimming and as small a body lift as possible.
If you're wanting to keep the ifs, there are lots of pre-runner type setups to add the strength for bigger tires, and some lift, but they are often more expensive than the SAS.
good luck,
8)
