4runner 95-02 yes it is an 8", yes it will go in any 79-95 pickup housing that was an 8"(not a 7.5 2wd), and lastly your 81 rear axle is a narow track. If you use uour 81 housing with the 4runner diff you will need to use your axle shafts as well. 86-95 rear axle is 3" wider and have shafts that are 1.5" longer on each side. The 95.5 up 4 runner is 3 "wider that that so 6" wider than the 81.
