Erik, thanks. Yeah, those ratings generally ring true, but are applicable for 6x7 film, which can't really be transferred over to how the same lens performs on 35mm systems.
I also don't need any lenses in this area, although a 150 or 200mm would be nice. The adapter is cheaper than either lenses suggested, and I'm not really interested in another Nikkor, since I'm well covered in the 50-100mm range. Maybe it's simply not worth it, although my curiosity is not helping and I have not found many resources online that shed light on how some MF lenses adapt to 35mm.
I'm also pretty useless at building stuff, but gosh would I like to repurpose my Rolleiflex's 75mm f/3.5 Tessar for my D810. I loved that lens on 6x6...