My tractors are something I always marvel over, besides the starter you don't need any power. I have an old Cat diesel that doesn't even have an electric starter! Uses a small gas engine (called a pony engine) to start the large diesel engine, and the gas engine uses a pull start, very similar to a lawn mower engine.
They always have direct injection into the cylinder as far as I know. Maybe in the early 1900's they did manifold injection but I don't think so.
It's just a total different concept.
How the metering is done (IE How much fuel to meet load) though may have been similar, I am not sure. I 'asked a friend' on this one, since I am really unfamiliar with diesels in general.
And there are some engines that are indirect injection (called IDI). I've been on the hunt for a 90s 7.3l IDI. They're gutless without a turbo, but slap a pair of turbos on and it makes a heck of a towing machine. But I don't know as much about diesels, partly because they just never break the way a gas engine will. I've rebuilt a few gas engines, diesels just seem to be made of tougher stuff.