Force experts I need your help before I purchase a 1990 120 HP motor for parts. From my service manual it appears in 1990 there was an A and a B model motor. The pistons changed size from 3.313 in the A to 3.375 in the B. Is there any other visual difference between the A and the B that I can determine which model motor this is without removing the head and measuring? I am currently working on a 1993 and need a couple of pistons. Trying to avoid having 2 motors both in need of pistons. Thanks for your help