OldIHC

Kubota made a 2.6L 6 cyl cast iron diesel. I have never seen one, but would be my choice if I were going to "diesel" a car. Provided I could lay my hands on one.

May be I missed it, but I never saw a good shot of the engine, I suspect that is a 4 cyl. The 6 cyl was based off the smaller displacement engines. They made a 4, 5 and 6 cyl version, later I think they dropped it in favor of larger displacement 4's.
I own a 3 cyl 722 that I made my APU out of in the 90's, and worked on a lot of the smaller 4's when I worked on manlifts. in the 80's and 90's.
Kubota made a "high altitude" kit for the 722 that had a little turbo not much bigger than a film canister.