When I got my car (after the misuse of more than one PO), the original belts were long gone, replaced by some godawful stiff "racing" belts that were damned near unwearable. I installed the hoop (can't remember what year is imprinted on it) and crab claws (modified a bit by installing a static shoulder belt as well). I'm sure I must have had some photographic reference else I wouldn't have chased them down, but I'm drawing a blank right now. When I get a moment I'll pull out the "Before you drive the 1971 Spider" sales brochure and see if that's where I saw them in a '71.
I took a quick look online and found a few pictures that showed the hoop in a 71 spider.