I've heard of people doing this quit a bit. I'm not sure of what's all involved, but I know one thing is the differencein actual width of the spring.
You'd have to either buy new perch's, or find a way to modify (widen) your existing. I've seen people mount the spring hangers on the outside of the frame also, seems to help with the over all ride. Mine's more of a trail rig, so I was never too concerned with the street ride.