I was at my local Tractor Supply and spotted a Kohler CH270 engine in their clearance section for $125, which is 75% off its normal price of $500. This deal is in store only , but can be purchased online for in-store pickup if there is stock near you. I checked a few locations around the country and it appears to be on clearance at all stores that have it in stock (price may vary from $125-$200).
You can see if it is in stock near you by clicking on "Check availability at nearby stores" under "Ship to Store". Then put in your zip code and check the box for "Show only stores with Pickup in Store available". When you click "Pickup Here" it’ll add it to the cart at the clearance price. You can’t see the clearance price without adding it to the cart.
According to Kohler this engine is a universal replacement that is compatible with a wide variety of lawn and construction equipment. I bought it to replace the engine in my vintage Troy-Bilt Horse tiller, and it should be a very easy swap.
https://www.tractorsupp