I believe the KT-4 was equipped with the Corvair engine. I've got a brochure that I posted somewhere here on the FORUMS, I guess I should go look up the specs!
EDIT: NO BROCHURE for the KT-4
However, at one time I wrote up a Wikipedia article on Kristi Snowcats and this is what I have on the KT-4 from the original Wikipedia page (it may have been altered a couple dozen times since then):
A large Kristi, designated the KT4, was built as an amphibious machine and was built in small numbers. It was powered by a modestly sized 6 cylinder Chevrolet Corvair automobile engine. Reportedly less than 20 of these KT4 units were built and they were offered in 2 series between the years 1961 and 1965. KT4s were designed for snow, sand and general ground use, while some units were built with the amphibious configuration and were designated as KT4A models. The KT4 was available with a fully enclosed fiberglass cabin, while the amphibious KT4A model had and open top configuration. There are no reported KT4s currently in Europe and no records of them have been found in either Arctic or Antarctic expeditions or research. It is possible that only 2 or perhaps 3 of these units exist. An un-restored open top version is known to be in Idaho, at least one enclosed version is reported to exist.