Single cylinder air cooled Kohlers were available in 7 and 8 hp, and have 7 head bolts. 10, 12, & 14 hp engines have 9 head bolts. The 10 hp has a flat bottom oil pan, 12 & 14 have a deep sump. 16 hp engines have 10 head bolts and a sump also.
All single cylinder Kohler engines used in IH Cub Cadets had 1 inch output shafts. Not sure what other companies used but suspect most used 1 inch also.
Keep trying to post a picture. Best way to say what you have. Even if you could tell us what color it's painted would help.