I've found this weird, but I have both shoulder belts and lap belts on my '71, but I can't seem to use them both at the same time. They don't look like the ones that a friend has in his '72 that have a little round thing that the shoulder belt connects to the lap belt, which then plugs into the seat. My shoulder belts and lap belts both have the same ends. So my question is, are they origional? They look origional to me as far as wear goes, if so, how do I use them both?