I would be cautious about the Mamiya Super.
They are really nice cameras.
Mamiya replaced them with the 645 Pro because, apparently, they did not stand up well to heavy use with the accessory motorized grip - and that grip was popular with the wedding pros that the Mamiya 645 line was marketed to.
The replacement 645 Pro had/has more robust film advance gearing.
So if the 645 Super camera was not used heavily with the motorized grip, it may be a great choice - I really liked the otherwise heavily used one I had for a while. I added a 645 Pro to my kit when I had the need to have a backup available. Then when it came time to downsize to a single body, I chose to sell off the Super, although either choice would have been fine.
All the lenses and the film inserts are compatible across the line. Some accessories have wide compatibility and for some (e.g. the trigger grips), it can be an interesting research project

.
The replaceable backs all work on each of the Super, the 645 pro, and the 645 Pro Tl.