Will I need to buy a diff drive shaft to accommodate my tractor for any tiller or are you saying to accommodate a yanmar tiller to my 240d?
If you find a Yanmar tiller be sure to get its native driveshaft and top link components as a complete package. Otherwise it will be difficult and costly to replicate any of these essential parts.
I was lucky when I got mine, the driveshaft was too short. I went back to the VN wholesaler and they said it must have been modified for a slip clutch so they gave me a driveshaft extender (common Tractor Supply item) to make up the missing length. You don't want to get into problems like that, that may be more difficult to resolve.
The 'before' photo that I showed the dealer.
'After' photo, in use with driveshaft extender bringing the shaft length up to normal. Yes it needs paint. Now 10 years later it doesn't look any prettier. But I had asked them for their cheapest tiller, and this cost $200 complete including that $20 driveshaft extender they provided. It works fine. That's the same tiller in my sig photo below.
(The pretty photo I put in an earlier post was someone else's tiller on a nice VN refurb).
Added: Use a common US tiller instead? Seems to me so long as it has the right length driveshaft, or larger so you can cut it down (simple), it will work as well on a Yanmar as on anything else. You might verify it will clear the rear tires lifted as well as down. So far as I know it was only the tillers made in Japan for their domestic market tractors (ie RS1400 tiller for YM2000) that are so close-coupled that they need that special top link assembly and everything else on the market is generic dimensions to fit anything.
If you haven't read this already - the US dealers had US (Canada?) made tillers and other attachments to sell with the US Yanmars. Then later when the VN refurb shops flooded the US market with 'rebuilt' (repainted) used Japan-version tractors, they normally included the tiller that had been with that tractor since new. So for a while there were a lot of Yanmar-Japan version tillers available here cheap. They may be hard to find now.
Photo - my tiller is the last green one. (But this importer went out of business a decade ago).