Success over the weekend despite a 2 steps forward 3 back approach in what I'm correcting.
So fully removed both mounts, discovered they are symmetric offset matching, so doesn't matter which side they mount.
On refit I worked the problem side first (PS) to get maximum header clearance within the fitment limitations, loosely fitted up the DS side, then locked up the PS mount then the DS.
This resulted in about a 10mm clearance which is far more gap than I had, so I believe this will fix this strike issue.
But part of the work also involved replacement of a damaged sump. I wasn't sure if I could get the old sump out with the mounts on. I proved I couldn't so had to take the mounts off again.
However followed through on this work with the engine raised and managed to remove the old sump, clean up, re-gasket and fit up the replacement sump successfully.
Second attachment of the mounts in the same sequence got the same result as above, so happy boy all round.
Last part of my work is to fit up a sandwich plate to feed my
oil cooler and 90 degree filter attachment fitting on the block and I'll have knocked off the major work I wanted to complete.
Then it'll be just the need to start refitting all the bits I'd taken off before a test run up and drive.