OZ built Mk1 cars used the AEG163 head with the thin flange block and 9FSAY engine numbers. Built up to the end of 68 including MK1.5 cars.
AEG163 heads were painted blue on the top under the rocker gear. Earlier heads were painted yellow and had some overheating problems but I don't think any of these were on OZ built cars. Most likely on UK built 1071 cars etc.
MK2 cars used the 12G940 casting with 12G1805 stamped next to the thermostat housing. These cars had the thick flange block and 9FXEY engine numbers.
Clubman GT cars also used this head block combo but the engine number prefix was changed to 1200 supposedly to rationalise the engine number codes. I think all it did was introduce another list of different prefixes to confuse us mere mortals not part of the BMC/Leyland inner sanctum. The last Clubman GTs are supposed to have used non S blocks with big journal cranks but presumeably still used the 12G1805 marked head.
There are some differing views about which cars had which blocks, heads etc during the changeover from MK1 to MK2 cars.
MK2 production didn't start until approx May 69, or at least no MK2 cars were available for sale until May 69. Were there any MK1.5 cars built in the first part of 69? Who knows.
My own MK1.5 car was built in the last part of 68 and is one of the last ones built. Car number is in the 4800 range. My own personal opinion, not necessarily correct, is that there were no MK1/1.5 cars built in 69. Others may have differing views.
Valve sizes, lengths etc are as DRMINI has said above.
Don't know about the later Metro heads except I remember reading somewhere that the Metro head 12G940 casting had the inlet valve throat shape changed to provide a sort of venturi effect to increase gas flow into the engine. Something to do with emissions, fuel consumption etc. The AEG163 head is a little bit like this too compared to the 12G940 head.
Hope this helps
Regards
RonR
