Great news! Glad you found it.
I did more research and found that I may be confusing part numbers with year of car. My 1949-52 Mercury Chassis Parts Catalog says the following:
8CM-6049-E is RH cylinder head for models 9M,)M and 1M, years 1949-51
1CM 6049-A is RH cyl. head for model 1M, 1951 year
8CM 6050-E is LH cyl. head for model 9M, 1949 year
8CM 6050-F is LH cyl. head with 3 bosses for oil filter mount, Models 9M-OM-1M, 1949-51 years.
1CM 6050-A is LH cyl. head for model 1 M, 1951 year
Your engine looks to me to have genuine 1951 Mercury heads and has the correct water pumps and belt configuration and width as the 1951 Merc.
Sorry for any confusion or anxiety I may have caused.
PS: Time to change that lower radiator clamp if hasn't been done already.