I'm your height and weight, but your sit bones are what determine what saddle you need, and yours could be closer together or farther apart than mine.

Having said that, I need a wider saddle. I've got three that work for me - Specialized Avatar in 155mm, Selle Italia Turbomatic Gel Flow, and Selle San Marco Regal w/steel rails. The Regal is the narrowest at 150 mm. I've done centuries on the first two with no problems; the Bianchi that's wearing the Regal is next in line for a century (I've already done a metric with it).

I'll add my recommendation for getting measured on the Specialized butt-o-meter before buying - it'll narrow your choices to what fits.