I have a set out of a 68 Sport Fury that I junked 20 plus years ago. There is a special square bracket that bolts on the underside of the rear package tray and that sorta holds the "dumb bell" looking steel rod in place.

I have them in a bag and if you need pic's I can pull them out and shoot you a few. I plan on putting them in my 68 RT Charger when I get to it.