Those stub axle carriers are special and look cast rather than machined? The top mounts are also different to any I have seen before. Moving the top of strut in that far would require different upright as well to correct geometry, so obviously designed together.
I have re-read 1971 Appendix J and it looks possible to fit different uprights and hubs- either under 'Optional equipment which may be recognised with a minimum production of 100 units per year- Reinforced suspension elements' or otherwise under 'Brakes of different type and/or dimensions, which may include larger hubs and spindles.'
The (not very good) picture I have of an upright shows a unit similar to yours, but maybe machined rather than cast. There is no clue as to when picture was taken, however.
MG- There seem to be lots of different types of track control arm- maybe worth something if could be proved they came off a famous car!
