using a wider purch will cause issues with the axle U bolts that fit around the axle and go thru the new (as sold available kits) plate that is under the springs (unless you the plate holes are suited for your width) connects all this together. this plate also connects the shock to the frame support.
Ps I moved my axle back 2 1/2'' so the under bed tank fit and I believe it looks better than the 1 1/2'' spacing.
heck you'll need a new drive shaft any way.
view of my 2 1/2'' offset saddle::
http://s67.photobucket.com/albums/h298/1951otter/?action=view¤t=Scan1_0001-1.jpg
