Since the Mamiya 7-II. like mine, has only a simple hot-shoe, it can use any flash. Metz makes an adaptor for its SCA system for generic hot shoes and the camera has a PC terminal. That means it'll work. But then, so would a 622 Sunpak.
My Metz 45CL4-Digital works just fine, except it has a tendency to get a little "hot." I can tone that down by lying to it about the ISO of the film in use. The coverage, laterally, is fine on 80mm and you can get a clip-on spreader for slightly wider lenses. Vertical coverage is somewhat more limited, but still adequate. (Well, what would one expect from that shape head and the lens setup?)