John Deere 490e Radiator Fan Not Going Back On

I had hired a mechanic to fix a diesel leak I had, and he did so by getting the fuel distribution pump rebuilt. As part of installing the new fuel distribution pump, he took off the radiator fan to have easier access. He told me he was going to return and reattach the fan soon, but I made the mistake of paying him for his work so far and he has been AWOL since. I have worked for several hours trying to get this fan reattached, but since I didn't see it come off I have been stumped. Basically - the fan attaches to a spacer then onto the engine block with four long bolts. The engine block has ~12 holes. There are 4 big holes that fit the spacer perfectly, but the holes have no threads and dead end in a metal plate behind them. I tried rotating the engine to see if the metal plate behind it moves but it seems to be one piece. The other holes do have threads, but are full of old rust and do not appear to have been previously used, and these holes don't line up properly. See these 30 second videos for visual: https://photos.app.goo.gl/95kiE5JBMoCvv1vN9 https://photos.app.goo.gl/LChgNVTZ1EFa6iL89 - bolts don't fit the old rusty holes https://photos.app.goo.gl/br3dz7jEiVRSZR2r5 - looking in at holes while engine is rotated