From tractordata, the C123 was put into the Super C, 200, 230, and 240 tractors. The bore and stroke was the same in all however, the compression went from a 6:1 in the SC to 7.x:1 in the 240. What did they do to get the extra compression? Domed pistons? My SC service manual is the one from Jen Sales and covers more than just the C-123. It doesn't give any variation for the C-123 head. The only thing left is a different type of piston.