Looking for examples of 3 Point Seatbelts in 1964 Valiant

I couldn't imagine an easy way to add an attachment to the top rail for a shoulder-belt, so did like most and used newer seats w/ integral belt. I have Sebring seats in my 65 Dart and plan to install some Mustang Cobra Convertible seats in my 64 Valiant. As you might guess, convertibles have the same issue and shoulder belts were mandatory by ~1968 so many options exist.