Steve, you might consider a 645 SLR for street stuff. The main drawback of the MF RFs is that the lenses are not very fast at all, which becomes a problem if you are interested in available light work or isolation by DOF. Don't get me wrong, I think the MF RFs haul a*s when it comes to scenic/documentary stuff, but... recently I went out with a mamiya 645AFD to a club and shot with the 80/1.9 and... oh yeah, big difference in what you can do with the light you have. Really nice results even with Fuji pro z pushed two stops and delta 3200, almost no grain in 645. And the 645 negs/chromes are quite a thing. Not 6x7 and certainly not as quiet as a leica or hexar AF but the camera is totally handholdable and appropriate for impromptu available light street shooting.
Just to give you something else to think about 😉
I also had two of the fuji fixed lens RFs, the ga645Zi (the zooming one) and the ga645W (very nice wide), loved them both. But again the lenses are a tad slow. I recall there was a fuji fixed lens 45mm f/4 that is quite nice but I can't remember the model, maybe it was ga645w or something like that. But f/4 is also pretty slow.
I use a mamiya 6 and love it, and there is the 75mm f/3.5 lens for that. But let me be honest, the thing is not so good for available light or isolating a subject by DOF, the lens would need to be at least a stop faster for that.
I guess I am saying, you might let the glass guide you to the body. I mean, you see all kinds of silly discussions about mamiya 7 versus leica... I'd say just think about the focal lengths and apertures you need and let that steer you to the camera(s) that is(are) appropriate.