Differences between OBD2 and OBD1 cylinder head??

[mightymidget 0]

Hi, can anyone tell me if they are different. I want to buy a 2nd hand head and recon it before swapping for my current worn out OBD2 head.

I think the only difference is the sensor on the duplex chain wheel (connected to the cam) for the OBD2 timing? Anything else anyone can think of?

Many thanks in advance, MM.