Why are you considering? Why aren't you driving to get it!
That is a beautiful original looking tractor. Good looking original tractors are getting scarce.
I don't but the five hour gag. I put more than five hours a year on mine just simply moving my tractors in and out of the shop once a month or so. If he only put five hours on it in 16 years, he has more money than sense. Just saying.
As far as engine work goes, it is a Tecumseh HH100 cast iron engine. It will run forever as long as the oil stays in the right place. Did it smoke when you ran it? Does it hesitate when you ramp the throttle wide open from idle?
Go get it and then let me know how the tests go.