Keep that 6 elements Rodagon, those 4 element Nikkors (your 75mm is also the same Tessar design) were made in the 60's as budget lenses, they are great performers stop down (f/8) at the center, yet nothing special at the corners.
All this only being evident if you print larger, on a typical 8x10 size, the difference is barely noticeable.

So, hold on that Rodenstock!