My vague recollection was that although the eccentric adjuster would rotate 360 degrees, it really only fit correctly in one position, and until I sorted that out, I could not get the sprockets over the cams.
I have just been talking to the head technician at SNG and he says unless the head has been skimmed a composite gasket will not work. Later cars , from the 60s have a modified adjuster which could be swapped .
Have you done all the measurements to determine you actual compression ratio?
When I did my engine, I found that the factory c/r was only about 7.5 to 1. So when I discovered the same problem you have, I shaved my head and went with a thin MLS gasket.
This now allowed the sprockets to be installed.
Thanks for all your responses.
All back together without any drama.
I used new bottom chain
Old top chain, it may have been marginally longer, but as it had come off the car I new it would go back on.
New tin gasket
After a fair bit of googling I decided on Wellseal gasket compound. It is more like a varnish consistency so you can paint it on thin, then let it dry for 5 minutes so you don’t have to rush to get it together.
Adjuster in the above photo dates from 1964, I believe.