I haven't seen any picture of the KMT90 4 spd, but I don't think we got one here unless it's called something else. I'd have to find a picture of one. The 4 spds we had in the 70s were B&W units called T18 and T19, both extremely stout truck units. We got some mediocre aluminum 4 spds in the 80s that were not well loved (SR4 and T4).
We got a TON of 3pd T90s in the states. Very plentiful and very cheap and mate natively to a Spicer18 (T18 in the list above). What you will find is 99% of the bellhousings are for Willys 134 motors with the starter on our passenger side (India's driver's side). The T90 was also used against the Willys Wagon 226 flathead which had it's starter on our driver's side. Early Scouts also used T90s but IIRC they also had the starter on the passenger side.
Going off the above, and assuming the KMT90 is not overly compatible with the T90 (perhaps bad assumption), then the bellhousings I'd be after would be that of a CJ500D. A good question would be if that bell was used on any of the KMT90 setups.
I'd love to put one of these engines in a Willys pickup or FC of some sort. I think that would be awesome. Knowing the US market, many of these Roxor's will have V8 gas engines in them in a few years, and there will be some cheap engines hitting the aftermarkets. To my knowledge the US never got a higher volume, small solid axle 1/4 ton diesel pickup.
I think Roxors will be cannibalized frequently for 4x4 builds of various sorts, diesel based and gas.