Are Heads Interchangeable?

[Fat Fender]

Are the heads on flatheads right and left, or can they be mounted on either side of the engine? I have a set of Canadian heads marked C7RA-A on each head (these were on a 47 Merc I bought in Canada). Below the "Made in Canada" at the lower center of the head is a "1" on one head and a "2" on the other. Does that indicate right and left? Can 59AB heads be interchanged right and left?
Thanks

 

[Barlea]

All answers are yes. You can even run 8BA heads backwards, or with one side missing altogether. ..B.