Its not a ’64 or ’67. The ’64 has a red Seahorse decal. The ’67 has a greenish leg I believe and different decal.
The ’65 and ’66 are very similar motors. If I had to gamble without doing research I believe it to be a ’65 as I believe the ’66 didn’t have that squarish outline around the decal, no border like the one in the picture.