Referring to Post 4: "Vintage-Looking Bikes with steel frame from new or recent construction with vintage look and characteristics may be used only if they are road racing bikes assembled using vintage components or replicated parts similar to the original as described above. In particular if the bikes are inspired by the design of road racing bicycles of the 1970’s and 1980’s, they must comply with rules a), b), and c) above, regarding shift levers, toe clips and straps, and brake cables."

A Varsity could easily meet the rules, a mountain bike would not.