re the rear rail.. IIRC there are no infinity stops on the rear rail, and I dont think they would fit right if you bought an extra pair. So how can you ensure that the lens is positioned in the proper place to use accurate rangefinder/scale focussing?
Q: does the 65mm f8 SA even cover 4x5?
Viewfinders: The finder for the Konica 58mm is nice and could be close enough to use with 6x9 or even 6x12. I found the finders intended for 35mm cameras to be too small. A DIY option is to get one of those .42x wide angle adapters and mount a flash shoe or similar foot on them. However if you are going to shoot 4x5 I reccomend using the GG so you can get proper framing.