help with a noise from the back of the car.

According to the VIN you have a 7 1/4" rear end (G 318). They don't last too long behind a 360. Pull the cover on the rear end and check for bits of metal and chunks of teeth. How do the spider gears look? If you are lucky all you will find is shiny gear oil. I had a '77 Roadrunner (318/ 7 1/4") that started making the sounds you are describing. Listened to it for a couple of weeks until I heard a loud bang while pulling out of a gas station and the car quit moving. The bang was the gear carrier breaking into pieces after a big chunk of spider gear worked its way in between the ring gear and the pinion...