A 35mm does not fit the 50mm framelines in the R-D1 viewfinder -- it fits the 35mm framelines. The R-D1's framelines already take into account the sensor's FOV crop factor for a given lens' focal length.
That having been said, the lens FOV is really only about 85% of the corresponding frameline area, as there's a focus-distance error factor built in by the designers, so you'll usually get more in the image capture than you saw within the framelines, but you'll almost never get less than you saw.
The one focal length/frameline match that I know of is a 40mm lens, which matches the R-D1's 35mm framelines nearly perfectly. I have the Minolta M-Rokkor 40mm f/2, which is a great lens and handles very well on the R-D1. Presumably the Voigtlander 40/1.4 is also a good option, but I haven't tried it.