Adding Headrests

I've searched here and other sources, and I can't find anything definitive on adding headrests to a 67 bench seat.

Since it was an option, do I just need the headrests and chrome pieces for the top of the seats?

Do only certain headrests fit properly?

Before I rip my seat apart it would be nice to know if there are brackets there to accept the headrests, or if I would need to make something, buy something, or get a 67/68 seat with the headrests already in it?

Anyone know, or do this already?

I want to add shoulder belts, and headrests for safety.

Its a split bench with the armrest.