Ok so My Giant Connect stock saddle isn't really working for me and I've been looking into getting a Brooks B17. I measured my sit bones via the foil on the carpeted step technique and came up with a 120 mm distance, center to center, between the impressions. Nashbar has two B17's saddles one being 175 mm X 275 mm and the other which is listed as a narrow measuring 155 mm X 280 mm. Both would be wider than the 140 mm I would be looking at in other saddles so which of these two would be the correct size to try out? Any thoughts or experience with these? I'd be putting it on a Giant AnyRoad with a relaxed riding geometry.
Thanks for any input.

I would try the Narrow first, personally. Brooks saddles measure wider than modern ones because you sit inboard the metal cantle plate in the rear, if that makes sense.

Given your dimensions, going with the narrow one would be a huge mistake. You will regret it.

Here is why:
The narrow B17, also known as B17N, is indeed nominally 155 mm wide.
However, its width at the widest spot measured in between the rear horseshoe-shaped metal frame is about 106 mm. Anyone with wider-spread sitbones would have them riding onto the metal frame, resulting in lots of misery.
My own sitbones measure 96 mm, and I have been riding a B17N for some 3 years now. The saddle is very comfortable (after I spent about 700 miles in the beginning of our relationship breaking my ar$e in), and still harder and stiffer compared to the regular B17. But it is not for sitbones measuring over 100 mm.

Your call...

Hmm, now I wonder what my sitbones measure.

Looks like it will be the standard then, thanks guys!