The higher quality enlarging lenses for medium format in that range are all 80 mm. optics. Most of them will cover up to 6x7 cm. negatives, even if the makers don't specifically recommend them for that application. Rodenstock and Nikon do. Schneider does not, but it works. The 75 mm. optics don't cover 6x7 adequately and are generally of lesser quality. For modest enlargements, it is unlikely that you'll notice much of a difference. If you make really big prints, or crop a lot, the differences can be quite noticeable.