Mystery solved after a divine intervention :)... that black "seal-shape" thing was petrified carbon deposit, the one with the gap is normal ... it was injector nr.5 so the missing glow plug might have some effect too.
If you've got the go ahead from your financial director i'd get the nice new one. I spent (and am spending) countless hours on it. I do get it about wanting to repair the original though.
Think that would be doable making various patterns maybe out of thin ply, been working with west systems 2 pack epoxy repairing a wooden dinghy but not cheap but cheaper than this...
https://www.lr-winches.com/Parts/Winches/Mechanical_Capstan_Winches/product/749/Fairey-Wheel-Chocks-Ground-Anchor-Set
if you find this useful perhaps you can make me a set too