The 4-115 is serial # 245 008-908. Built feb 7, 1974 per the build card. looks like this has 7/41 bevel gears.  

The 1750 serial # 211 492-437. Built Nov 11, 1968 per the build card. Looks like it has 8/51 bevel gears.  

The 4-115 is a drive train only the rest was missing when I got it. It was a parsons cable plow at one time. not sure of the history on this tractor.  I would like to find a 1955 to put the 4wd on. Are the 1955 rear ends  the same as a 1950 or are the bevel sets different?