The front axle that they used had an offset differential. They cut a hole in the side of the transmission, welded a plate to the housing and then installed the gearbox with shims to get the correct backlash. Drive shaft ran down the side of the tractor.
I have a copy of the build cards for the first experimental Oliver 1800 and 1900 Four Wheel Drive tractors. The 1800 was built on November 27, 1961 and the 1900 on the 29th 1961. One went to Green Giant and one to Del Monte and used in their rental fleets, then brought back to the factory to correct anything they had concerns with. Both were sold retail and are now in collectors hands, 1800 in Minnesota and 1900 in Ohio.