Here's a weird machine

So, I am new to the forum, but I don't know where else to turn. I have a very specialized piece of equipment that I use for research. It is a forage harvester with a flail mower on the front used to harvest research plots. It has an old Wisconsin Robin motor (Model EY27W). The machine itself was manufactured by Swift Scientific from Canada which is now out of business. I was approached by someone who had some money to spend and offered to replace the engine. My question is how do I know if I have the right size of engine, the right mounting bracket, the right shaft, etc. I know just enough about small engines to get myself into trouble, and my money needs to be spent by June 1, 2020. Any help on the matter would be great! thanks.