Like I was saying, the back should drop an inch or so. I have SS springs and needed to do the same thing but did not want to elongate any of the holes in the body. I doubt its a problem to do so but I wanted to be on the safe side and got adjustable hangers. It gives the same effect as "flipping" the hangers. I got mine on Ebay but Mancini also has them for a little bit more.
http://chucker54.stores.yahoo.net/manciniracing20.html
Also, See my post #7 on this thread for an illustration of how they work...
http://www.forabodiesonly.com/mopar/showthread.php?t=56273