My brother has a 1945 HD7 with a dozer that he also used for farm work. Good tractor, but the final drive gears are the weak point in the system. Brother had to replace one drive gear; finally found a good used one in a salvage yard a few states away.
The HD7 should have two large batteries to turn that engine over for starting. The engine exhaust is definitely not clean, so it is nasty to use inside a pole barn for dozing out the winter accumulation of manure.