If they are available, no reason why you can't simply install longer front spring hangers to move the axle back. Now, here's the disclaimer, you need to double check that you have enough driveshaft spline left if your axle is moved rearward.
Thanks Mike, as far as driveshaft goes I am good there and part of the reason for wanting to move it back is to keep from having to shorten it. After reading those links I am still as confused as before. Seems everybody has their own take on how to do it but spacing the front hanger back is the most common and agreed upon method.