rear seat belt holes 64 dart

Welcome there Lou. Glad to have ya here so we can try and help ya where you need it. I dont know but by the sounds of what your asking, the 64's didn't come with seat belts? One of my other 63 cars didn't come with em so maybe yours is the same. Seems like a set from a 65 or up should be a good graft. I've read before here that there should be indentations where the seat belts should anchor to. Just athought. If you car look under the car in the general vicinty and see if you can see a reinforced area, that may give an indication to where they might have went. Might have been an option in those years.
Small Block