Cheap Chinese Air-Cooled Engine Powering a Full-Size Tractor

This is amazing. A full size Massey Harris 33 tractor powered by a cheap 13 hp Chinese air cooled engine. The owner simply put a chain sprocket on the input shaft of the tractor's original transmission, and a centrifugal clutch on the engine. He's using it for actual work too; not just putting around for fun. Hmmm. I have an old flat-fender Willys jeep with no engine... Seriously, I have been thinking about getting one of these engines. Harbor Freight had them on sale for $350, and I found a 25% coupon code I could apply to it. Then shipping and sales tax brings the total to approximately $305. Before buying though, I decided to look on Amazon because they often beat any other deal I can find. Lo and behold, here's one for $280 shipped!