Who out there makes these items - who are my options?

I run a mk2 Granada with an arse end that is not too dissimilar to the later Sierra AKA taxi suspension.

Ideally I would like someone to fab me a 6 degree set up with strengthening and rose joints where required but it obviously is not a Sierra and so will be a one off.

From what I am asking there will be no manufacturing / conversion measurements or datums and certianly no jigs available to aid the work - who can I trust to sort out the arse end geometry accordingly who understands it properly without leaving me a bag of poop?

All replies and info very much appreciated