If this is the late-50's 820 were talking about, yer right, it's VERY heavy. It was the largest, most powerful 2 cylinder diesel John Deere ever made. It evolved from the 80, through the 820 to the 830 which was the last one before JD gave up on 2-lungers.
I'd LOVE to have an 820 or 830, preferably pony-start. The starting procedure on those beasts just fascinates the heck out of me.
Problem is, I'd have to buy a new truck and trailer to haul it, and there wouldn't be room to turn it around on my little patch.