The fuel tank from the Diesel engine was relocated to the original location of the battery and the battery was relocated under the seat where the old gas tank was located. A different muffler was also used.
It is a Chinese made clone of the Yanmar, I bought it on ebay. The engine runs great and it was a better option than trying to rebuild the old Kohler... The 10.5 HP diesel pulls better than the 14 HP Kohler.
Man oh man this is exactly what I need to do to my 'ol S-12 seeing as how it spun a bearing the other day. Did you do a build thread? If not what part number does the engine have and how well did the PTO and hydraulic pump shaft mate up? Please shoot me a PM if you didn't do a build thread as I really need the info! Thanks!