In the M3 character library is a character called "Mike 3 to Mike 2 ". This is Mike3's head on Mike2's body, as far as I know. If you use this, you should be able to use Mike2 clothings and Mike3 headmorphs.

The product description says:

Mike 3 to Mike 2 CR2 and OBJ

• Backwards Compatibility for Use with M1 and M2: - Poses
• Clothing and Accessories
• Compatible with M3 Head Morphs