[FFR428]

66/Feb/26 and 66/Feb/13 or if it's a D 66/April/13. There were some subtle differences. On the exhaust port some have a inner vertical "lip" around the right side of the port and some don't. Both big and small R heads have the lip at the top of the exhaust ports tho. All were cast themactor humps. Some were cast at the Cleveland foundry and some the Dearborn foundry. I remember reading somewhere the vertical lip on some was for the Fairlane applications exhaust for a little extra "meat" on the port surface. If the date codes are both B's I'm sure they are a matching set. Heads were heads and I'm sure while picking them off a pile for assy guys weren't looking at the minor casting differences in all cases. I'm sure they'll be just fine as is.