What exactly is the 350ULR? The only ULR variant I know of is being operated by Singapore Airlines (Air Lines? 😁
and I just don't see Delta operating a 309 seat airplane in a 161 seat configuration (as well as deactivating the forward cargo compartment which Singapore also did in order to fly direct to/from the US). The -1000 would be nice and gets us a bit of a range bump.