Can anyone advise me is it OK to remove one rocker shaft from the head and leave the other bolted down to replace the Valve lash adjusters it looks like it would be to me but just in case.

from memory I think its fine to do it that way

Yes aslong as you undo it evenly so you dont warp anything.

Thanks for that I will give it a go.

Hi folks I have discovered that this is the only way to do this job I thought the 6G74 was the same set up as the 6G72 in my old TS V3000 which is the rocker arm caps holding the camshaft in position but no the 6G74 has blocks built into the heads and do not separate like the 6G72