I'll second Ed's info.
I have a side dial (one) for the RZ (can no longer be upgraded by mamiya for ProII, but some modded units are out there)
The double top dial FE701 is made later (Pro II era) but is backward compatible with earlier plain ole RZ
My side dial unit is excellent and offers spot or average modes but will go to spot mode if the meter determines there is a wide dynamic range in the frame.
I believe both of the metered finders offer stepless shutter speeds when in Aperture Priority.
Ed, is that correct?