Rather than an impact wrench (which I think is what you mean by air wrench--it sounds as though you're talking about rechargeable electric ones, not pneumatic ones that require a halfway decent compressor to use), you may want to consider a breaker bar. 140 foot-pounds of torque using a two foot breaker bar is seventy pounds of force, well within what most people can exert without undue strain (if only by stepping on the end of the breaker bar). The impact wrenches do work pretty well, though, and are definitely quicker if you're going to be changing out wheels frequently.
