Adam, I initially replied with the same response, but then after looking around a bit, I got the impression that maybe it was just the post-00 tacos that got the 8.4.
I always thought the change was made when they started calling them Taco's, but I just wasn't 100% sure.
Ary you could be right I just always assumed it was for all tacos. You can look at the weld on cover on the housing, there is quite a difference in the shape between the 8.4 and 8" because of the bearing girdle. Here is a good link to toy diff info.
I don't think so. Pretty sure they both use an 8" ring gear, but not the same rear end, unless your Taco is a 2wd...that page makes it seem that the 2wd Taco might be the same rear.
1995 Suburban (big and slow)
1989(ish?) F-250 (doesn't move)