Here in Oz, bush cabs like mine are virtually standard on all dozers that work clearing vegitation for operator protection. Usually, they have down bars that connect between the front of the cab and the radiator to give more protection and mesh side panels. They are built by after-market engineering companies and mine would have been fitted along with the higher capacity fuel tank when the tractor was new. This holds about 50 gal or 220 litres. Another modification fitted is the Cat dry type air filter, using a purpose made cast iron adaptor.
John