Shorter springs, in general, don't flex as well as longer springs, so if you're building it to wheel, that probably isn't the best route.
As well, moving the axle too far forward won't allow you as much up travel, because your axle will hit the arch in your frame instead of having all that room it did where the axle was.
Your best two options, IMO, are tube the rear, or find a SWB.