There is a 20 HP V Twin version of the 10 HP Yanmar/China clone single cylinder diesel that's been readily available on eBay for a few years. That engine has been put into a 110 that's been on this site. If you can find the V Twin, it would be perfect for the 140 if you could:
Allow for differences in the length/width of the block base between the K321 and China diesel.
The hight of the crank vs. the K321.
Adapt some sort of stub shaft to the flywheel/ blower end to mate up with the 140 driveshaft. There are three or four small threaded holes on the China diesel to mount the recoil start but I don't think they are big enough for a stub shaft.
I have to check if the bolt holes on the other end are universal to fit the electromagnetic PTO. The oil filter is about even with the crank center, so it looks like it will clear the frame, unlike the B&S Vanguard conversion, where it has to be mounted remote or not at all. The right side frame rail would have to be boxed out to clear the electric starter.
These have been good engines for me. I have two 5KW generators with them, and another that will go into a Bolens 1050 tube frame tractor for a future project. I love the idea of the V Twin in my 140. That engine has two of the same cylinder heads of the 10 HP on a common 90 degree crank. It is still air cooled, so you don't have to worry about space for a radiator. Anyhow, the pushrod K361 is still going into my '69 140. It will be a lot easier to find another 140 than the V Twin China diesel. They are not that common yet. I have a photo somewhere that I will try to post. I just don't have it available in time for this thread.
Stephen