Wow I am shocked. They removed the 8 hp from the grillo g85d a couple of years ago. I guess the 107d diesel wasn't selling, and people were moving up the the G110 diesel.
I am sure they would mount a KD350 (8 hp) diesel if you wanted it.
The Kohler/Lombardini diesel engine (KD series) does not meet current EPA regulations. So essentially they are being phased out. BCS no longer sells them in USA with that engine as they are unable to import them. They are still in production and sold in Europe though on BCS and Grillo. I know Earth Tools has a supply of those diesel engines, how many I have no idea. They will eventually run out of stock (I think). The 8HP diesel on Grillo G85D/107D (Or BCS 739/732 and smaller) in my opinion is a bad "fit". Reason being the engine is so heavy for that size machine. Handlebars are too short. In about a month Grillo has the 2017 models out and they include 3" longer handlebars on G85-107D. That will be really nice. The only small diesel engine (that I know of) that does meet current EPA regulations is the Yanmar, which are good engines. But the problem with them is they are about 30LBS heavier than the comparable Kohler/Lombardini (KD420/440). I have 2 of those engines (KD440)(one on 853 and the other on G131) and I love them. But if you add 30LBS to it, I would probably prefer some other set up.