If a picture is worth a thousand words, then the photo Rex Keep snapped of Frank Shorter striding alongside Matt Carpenter around the Vail Athletic Fields on a summer day in the late 80s has to be worth at least 8,150. “We had a couple days a week that we’d all try to get together for training runs,” Keep said, speaking of the old Vail Running Club he helped start. “When Frank was in town, I’d take my camera and try to get a few shots.” Keep’s…