Toyoda did in fact offer a 4.88 ring and pinion. The aren't as popular as the aftermarket r&p because they aren't easily found and Toyota is the only place to find replacements. I believe that the carrier and possibly the housings are different than other comparable 3rds. That particular 3remember in the 2nd pic by EricB is for a 8.4 taco axle and will not bolt into a 1st 2nd or 3rd gen Toyota.
to go with this i have read that several people said the housings aren't different at all, just the internals of the third, i think kyle_22r knows for sure
