The 300 series round nose tractors were built in 1956 & 1957. The gas engine is 148 cid, tractor generally rated 30-33 hp PTO & 28-30 hp drawbar.
Engine serial nr 110M + 5 digits is the only one I've have seen in the gas 300 series. Doesn't mean 110N + 5 digits isn't common, just haven't seen any.
Case parts manual R.I. A324, lists the rims you have for models 302 & 312. I don't know if they will fit other 300 models.