My dad sold Allis Chalmers from 1959-1987...
Our church purchased a 5020 in around 1980 or so to mow the grass...
Since then we have worn out 2 decks and now use it with a 6' Bush Hog rear finish mower...
The tractor has around 2600 hours on it and is bullet proof...
Yearly maintenance is all that is required...
Still does not use any oil...
With that said the manufacturer of that unit, Hinomoto, is out of business...
They utilized a Toyosha diesel engine...
I can attest to their durability and performance...
Parts may be questionable...
Oil and fuel filters are not an issue...