An 80mm El-Nikkor is made for enlarging 6x6 negatives, so there should be no problem with coverage. The 50mm will cover at macro range.

I once bought a 60mm Componon which I didn't need only to get the lensboard it was mounted on: A Technika III 5x7" lensboard! Someone must either have been doing some extreme macro work with a 5x7" camera, or have use a converted camera as an enlarger...