Does anybody have a diagram of this?

Hi,
Yes I do have it posted on the Internet at:
John Deere decks by crigby (http://opebycrigby.tripod.com/decks/jd80sdeck.html)
It will basically be the same as the 46 on the 160, etc. machine.
That is a rare machine with a Yanmar diesel engine with an ingitiion and a carburetor. With good maitenance it could last a lifetime. The slightly newer 280 and 320 are about as rare.
Peace,
Clarke