Yes if you have the right bellhousing and the later version. There are 2 or 3 variants of it. The early ones before 60 something i think, and the ones behind 4 cylinders have a shorter input shaft and won't work with a 6 cyl. I have both versions and the shorter (4 cyl) is 7" input stickout and the longer (6 cyl) is 9 1/4". Also you have to figure in the fact that the t90 only bolts to a spicer 18. In order to get a Dana 20 to mate you need a adapter. AA makes one I think and I know Novak does. And in case you didn't know the Spicer 18 has the front and rear outputs on the passenger side so a rear axle with a passenger pumpkin is required. My 71 scout 800b had a amc 232 with a t90. I swapped in a 258 though. Unless you have the correct trans and bellhousing is will probably not be the best swap due to not being that strong and needing adapters for the Dana 20.
If you want a 3 spd the t15 is the best. And they don't sell for to much. The t150 ain't bad either but its still not as good as the t15. The t90 and t150 both have unsynchronized first gears whereas the t15 is fully synchronized. I've had all three and the t15 is definitely the best for the money.
1979 CJ5 408 AMC dana 60/14b, T18, d300, PSC hydro assist
1948 Willys CJ2a LS 4.8/sm465 scout 44's