Max, I am interested in the same information. If you track it down please post it. Look up Gehl in the group. A few people have made the same comment that you have and a parts manual was posted in 2020.
I know the company was Oakes Manufacturing, Inc. Industrial Park Oakes, ND 58474
701.742.3284 Somewhere in the group it is mentioned that the name changed to Prime Mover at some point. Before the internet, I used to call a library to get information. Oakes ND probably has one. Try giving them a call. - Mark
p.s. I will be uploading my father's Rounder manuals etc. to Scott's (SWR - group owner) shared Google Drive soon. I have already uploaded his Onan manuals.