The 6500G was used in the Cat 40 tractor
The 9500G was used in the 70 tractor

The 9500g was the engine in the Seventy tractor. Lots of cubic inches and a very thirsty. Most of the Seventies in California had there engine replaced with D8 diesel engines.

That is the main tank, same size as D13000 power units. 70 gallon capacity. Original owner did not use the fuel tank, They had copper tube hooked to fuel pump and stuck it in a 55 or 110 gallon barrel. Either got tired of pouring or pumping fuel into the tank I guess.
Another interesting thing these engine have cross flow heads and have the rocker arms crossing each other. One real long rocker and a really short one.
Downside of these engines with large bore, they have only four head studs. Most seem to have serious head gasket leaks.

see the a Cat 9500G PU thread, not the greatest picture, but.

Was the cat 65 the same motor

It is basically the same, it was a 9000G engine. The front timing cover and front motor mount are different. So the are not directly interchangable.