Outer Limits 4x4 Board

Can anyone tell me if the 2H head changed between '80 & '89? I'm aware of the 3 different blocks but wasn't sure about the head. If they did change it, are they interchangeable between early and late? Thanks

I have never had a problem fitting late 2h heads to early blocks and vice versa.The rocker gear and push rods are different early to late but the rocker posts fit either head.