Nice to hear it is being saved. The correct way to say the model number is, "One Twelve" This model with the D-315 is the same basic engine engine that a D-4 6U and D4-7U used. It always baffeled me a little as to why Cat designated the smaller graders with the bigger numbers back in the day. The "Two twelve" from about 1948 and well into the 50's used the D-311 engine which is the same basic engine as the D-2 4U and 5U. My neighbor has a Two Twelve that has direct electric start. Suffix is 79C-42 which is a 1955. This option is rare. I wish he had some road work as I love to run a grader and have run the 212 in the past. The model 12 of the era used the same basic engine as a D-6.
With that much wear in the bearings you are on the edge, and I would replace them with a new set of standard bearings.
You can also look on the left side of the grader frame near the front where it bends downward to the front axle for a Brass serial tag. Unless the engine was replaced, the number should be the same for the engine. Dandy Dave!
Most of my Money I spent on Mechanical things, Tools, and Woman, The rest I wasted.
Always remember, These old machines are like a Woman, It is the little things that count.