There was a discussion on another thread here about seat belts with integral shoulder.
The 74 model year came factory that way.
Here are some pics of what they look like for those who may be interested in the change from separated pieces. Both belt mounts are ratcheting. I believe the plastic side panel is the same as earlier models with exception of a slice and slotted hole for the belt to come thru. Rectangle filler cap bolts to the belt mechanism.
Mike