seat belt questions

[chewychevy67]

i have removed a few sets of 67 belts and was wondering if there should only be one plastic sleve on the inner latch lap belts like in the picture or one on each side? if only one what side does it go on? been years since i removed them and before digital cameras and i keep seeing sets for sale with only one of them. also when optioned with shoulders do the inner shoulder mounting plates go under the lap mounts so the plastic sleve can go on top? thanks for any help on this.