It's not as simple as the outside width dimension of the saddle relative to your sit bone spacing; some saddles of the same outside width start "rolling off" closer to the centerline than others that are relatively flat almost to the edge. You should avoid saddles that begin rolling off nearer the centerline as your sit bones will likely be on the slope.

I'm 71 and used Brooks Professional saddles almost exclusively until a few years ago when I began experiencing numbness in the perineum soft tissue area and went shopping for a saddle with a center cutout and fairly flat surface with the rolloff beginning a centimeter or so outboard of my sit bones. For me the answer has been the Selle SMP line. There are models with different widths, degrees of padding, etc.

YMMV.