I tried the old "turn the leaf springs around" trick and it didn't work for me - the rear axle ended up being about 1" too far BACK in the wheel well opening. Here's a pic of it before I got the bed on and realized that it was too far back:
http://i48.photobucket.com/albums/f214/tkeahi/novarear015.jpg I ended up taking the rear end back off and drilling new holes in the spring perches where I wanted them. Some good advice (that I wish I followed) is to drill holes about 1" apart in your axle perches/bottom plates before you put them on so that you can tweak the location once you've got everything back together.