Oliver 70's with dual exaust

Also, I'd like to find a 37 to 39 model (as my other tractors are from this era). Are there any real differences between the late 30's models and the mid 40's models?

The first year of production for the model 70 is 1935. The first models had the cast iron grill, in 1937 (at S/N 216 926) a change was made to the Styled sheet metal grill. The hood, engine and clutch side panels were changed at the same time. The serial number for the tractor is stamped on a plate that is attached to the side of the engine crankcase. Early tractors had 5 gear engines ( 5 timing gears at the front) later had 3 gear engines, changed at S/N 223 151. the last year of production was 1948.

Both engines were built with a manifold that has two outlets. From the factory it had an elbow at the front with exhaust going into a muffler into a elbow that was mounted on the rear outlet with a plate between the elbow and exhaust manifold outlet. As you can see it was easy for someone to install two exhaust pipes by eliminating both elbows and installing a pair of flanged pipes. A tractor could be ordered less the muffler. There was not a factory option for the dual pipes.