The decks are different. Gearbox is different for sure, since the gas engine turns 3600 RPM and the diesel version only 3000 ish, so the gear is going to be a little different. I don't know about the mounting points, width, length, pin size, etc. so I can't comment on that.
If they were the same between the two, kubota wouldn't have designated 2 different model numbers. They, like many manufacturers, prefer to use one part instead of two if possible.