Depending on how much patience you have you will probably want a tank. Tanks are cheap and you have plenty of options of mounting somewhere on the 4runner. I know the dual ARB compressors (yes those are the expensive ones) can fill up tires no problem and they are faster than my 100% duty cycle VIAIR with a 5 gallon tank, although my compressor is about 8 years old... There are other options out there too, look at the CFM's that the compressor pushes out and the duty cycle along with the amperage - the tank is nice because you can build up a reserve of air to fill up tires quicker, but again if you have the patience then you don't have to have a tank just a decent compressor.
I would do a search on pirate4x4.com as there a million threads over there on this very thing.