M carb

There are several possible anwers here. A true M carb has 47387db or 50983db on the brass tag on the throttle body. If your numbers match then someone has switched bowls on your carb at some point in time. I see this often on carbs I rebuild. You are correct, though, in saying the choke shaft should be "away" from the engine. Models which have the choke shaft "in" are as follows with the carb #'s ( the numbers may be a couple digits off as I am working from memory).
Super H #358065r91----300/350 #361525r91---Super M #356948r91----400/450 #362173r91. These are the only tractor model carbs which will bolt up to your M. Although the I.H. carb bowl is pretty much the same from the super H all the way up to the C-301 856 engines(with minor differences). Some onne could even have used a combine carb bowl or from a power unit.

Good luck. I hope I have given you enough data to solve this puzzle. If not, post back!