Austin western model 55 grader

I have a Austin western model 55 grader with a u4 international engine. I was wondering how many were built with this power unit? The transmission has ih castings, is this a w4 tractor transmission? How many model aw 55 graders were there built? I have this pegged as a late 1940 or 1941 model from the ih casting codes. Any input would be appreciated. Thanks.

Austin western model 55 grader