I did a similar engine replacement on my Deutz Allis 914 Hydro ( made by simplicity, and essentially the same as some MF tractors). I had to install a replacement Kohler 320 shortblock in the frame. The drive shaft in my tractor bolts to the flywheel , so I didn't have to match the engine shaft sizes ( and there are lots of shaft sizes.) The only problem was that the oil pan on the replacement short block did not fit down into the frame. I went on eBay, and bought the only two other size oil pans I could find that bolt to a Kohler 320. One of the two fit nicely , although I had to make a new mark on the oil dipstick to indicate full. The replacement short blocks do not have a balance shaft inside, so they vibrate like crazy ! But, 14 years later, it still runs like a champ ! ( And a Kohler 14 hp. engine puts out a lot more horsepower than a Tecumseh engine of the same power rating , especially if the Tecumseh engine came in a Sears mower!) Good luck with your project !