Late in 1963, The GoldeBriars recorded “Sunshine Special,” the group’s adaptation of the traditional train song. Curt Boettcher – the male vocalist in the line-up and also its major creative leader – would later make sunshine a specialty; his shimmering California-pop productions for the likes of The Millennium, The Ballroom and Sagittarius have all gone on to attain cult status. There’s not much of that baroque psych-pop sound on Now Sounds’ Walkin’ Down the Line: The Best of The GoldeBriars (CRNOW52), the first-ever retrospective for the short-lived folk unit. But this compelling…