I would go for option 1. I have never seen an original rose joint in the inner TCA connection. I did read some reviews on the first Cosworth that it was supposed to have this, but there were complaints and Ford apparently changed it to a normal rubber bush. But these arms cannot be from a Cosworth anyway. So I'm not sure if these rose joints are original. Anyway, if they are in good condition I would keep them. They are superior to a poly bush in handling.

For the outer ball joints I would clean and re-grease it and replace the boot if there is no play in there. Having something special made can also make you worry if it will be strong enough. You definitely don't want such a connection to fail while driving!

I don't think you will be able to clamp the arb bush enough to go from 28 to 26 mm. But even if you would, the pressure on the arb would be quite low, so the functioning of the arb would also be not great, as it would be able to move inside the mount.

BTW, can you respond to my questions on the steel diff in your project thread? I'm really puzzled by that diff!