Timing is everything. I was cleaning last night and in this box were  some copies I had made several years ago on tractor models made by the Cleveland Tractor Company. This sheet was given to all Oliver dealers  when they received a master Cletrac parts book in 1945. I have the one my employer had. Only the first 82 tractors in 1939 had the IXA engine. I also have a General parts book and it has parts for both engines. Hope this helps. I have one of those books also. My brother-inlaw has it now. John