I think I can start to see why this would be no simple bolt on task. I might not have the right PA engine, but cannot see any reference to a later head in the parts images.
Assuming I've got the correct PA engine, the image below shows a PA head gasket next to a grey motor one.Not quite the same scale, but you get the idea.

- Vauxhall versus grey head design.png (144.69 KiB) Viewed 3637 times
The PA has 14 head bolts, whilst the grey has 15. You might get away with most of them, but the carb/inlet side centre bolts on the Vauxhall line up to the grey's water port (
red circles). The Vauxhall's bolts all appear to be inline, whilst the two outer carb/inlet side bolts are offset in the grey (
blue circles).
The water jackets would also be interesting... not much line-up (at least by eyeball), and looks to be waaay out on the sideplate side (
green circles). This is probably the reason for the external coolant manifold on that video.
Cheers,
Harv
327 Chev EK wagon, original EK ute for Number 1 Daughter, an FB sedan meth monster project and a BB/MD grey motored FED.