Monte Carlo rear end

I have a 72 Monte. I sold the car to my kids friend and he had it for about a year. I now have it back because he couldn't finish paying for it. I've never done anything to the rear end except replace the springs. While the kid had it, he told me he was driving on the freeway and something fell off of the rear end. My son now drives it and he says it sometimes feels like its fishtailing. Can someone please direct me to a site (or send pictures) of a complete rear end? Any help is appreciated.