68 Cuda Mini tubbed with back seat - How to ?

That is the issue. The seat frame will need to be modified, upholstery will have to be modified and re done.

I also see that the mounting points for the folding seat back have been moved. None of this will be easy and all of it should have been done before the bar went in.

You will probably need to have this professionally done.

All custom work.

Bingo. The frame needs to be sectioned. Removing some material is necessary too. I could see chopping and rewelding the frame,that would be easy with carefull measurements. But unless you know upholstry youll need to farm that out.