The 3-speed t-90 was the only transmission available in the '61-'65 Scout 80 line. With the 800 like yours there were more options to choose from including a 4 speed manual, a borg warner 3 speed automatic, the larger 196 I-4 in addition to the 152, and a 266 sv8. Also, previous owners swap components around all the time. So for anyone to say that any given IH vehicle has "only this" or "only that" component installed is foolhardy. That's why it is so important for every binder owner to make positive id of any component presently on their vehicles that is in need of service. I'm not at all surprised yours has a 4 speed in it. Count your blessings on that note. The t-90 3 speed is garbage. The later 3 speed with synchro 1st gear and better spacing between 2/3 that was available in Scout II's is much better.