The Mamiya Magazine 35 user manual cited make absolutely no mention of interchangeable lenses, only interchangeable "body units" (magazines.) This is the camera shown on the web site.
Ads from the time make no mention of interchangeable lenses: http://store.vintagepaperads.com/servlet/-strse-6578/1958-Mamiya-C-Professional/Detail
This website specifically describes the Magazine 35 as being a fixed lens model: http://herron.50megs.com/rangefinder.htm
Is there another Mamiya Magazine 35 that has interchangeable lenses?