Hello I am confused as to what motor I have it is in a 1961 chevy apache 10 4x4. I asume it is a 235 but not positive,I've heard it could possibly be a 261. I cant read the numbers on the block but i did get the numbers of the head and hope someone out there can help me out. here are the numbers on the side it reads, 23 848 850 and on the top it reads con9, K 21 D, and GM23 hopethis will help somone help me as I am in search of a new headas mine has a major crack in it. thanks for your time