Yep, it turns out that its the later type of engine ID tag. Turns out to be a 807-04, originally fitted to a Renault 16TS, 1565cc, 8.6:1 compression. Just as a thought, doesn't the 821-30 have high compression (domed) pistons? In theory (amateurish) wouldn't it be possible to swap the head on my original block and the cam? My engine has only done 51k miles (no idea if that's genuine) just musing if I have a poor man's option to the rebuild.