Holy crap, that is a good deal! Almost too good. 250 is what you'd pay for each gear set new, and then add bearings on top: the guy is discounting it over 50%. Go for it as long as you are sure there isn't anything wrong with them.
Assuming you stick with 33's (Easier on the front end of your truck) then yeah, the 4.88's are going to be real nice.
Baby Beast 2- 1999 4Runner SR5
Baby Beast -1987 4Runner SR5-Gone, but not forgotten