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There are just too many variables to accurately answer your questions. Bear in mind we in Canada did not get the same buyers guide as in the US. Our guide called the 300 a 2-3 plow tractor and the 400 a 3-4 plow tractor. I don't remember what they called the 350 and 450, however the 460 was called a 4 plow tractor and the 560 was 5 plow. I always considered the 300-400 ratings far more realistic than the 460-560 ratings. Two factors come into play here; 1st by the mid 1950s and into the 60s, IH management was starting to completely loose touch with reality and secondly farmers were gradually starting to move from trailer plows to mounted or semi-mounted plows. Draft control on the 450 and 560 hitches made a huge difference in the amount tractor ballast, versus number of bottoms and type of plow. Now, I will agree those first IH draft controlled hitches were mickey mouse affairs, but they did work when the tractor was new. By the time IH got 06 tractors on the market they had it right. From 06 through to 86 series tractors IH had the very best draft controlled hitch on the market. That left only one problem, and that being user ability. On your question of how much the tractors would pull, I don't ever recall IH making any statments in guides on that matter. There are just too many variables to advertize what a certain tractor would pull. IH management were not the sharpest knives in the drawer, but I also don't think they were stupid enough to say a 560 will pull XXXXX XX tons. Basically you were refered to Nebraska tests and that controlled envoirnment and testing. Remember also the tractor with the most drawbar pull was not necessarily the most efficient tractor to farm with. You go back through Nebraska tests, two factors they give you that are very important; horsepower hours per gallon of fuel and PTO hp in relation to drawbar hp. It's one thing to have big hp, but takes an efficient power train to put in on the ground.
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