Hello guys, I have a question about DC heads. Probably a dumb question, but I'm new to building a 4v. I recently picked up a bare set for my son's car. I remember reading somewhere that the revised heads had a "driver side" specific head. Both of my heads say 2C5E-6C064-DC on the side. Just above that one says 27 S73, and the other says 30 S73. Is it safe to say that the 30 S73 is the driver, and 27 S73 is the passenger?