On the old Chevys the axle is about 1-3/4 inches ahead of the center bolt. Plus the AD trucks always looked like to wheels are too far forward anyway.
You can't reverse the springs,just re drill the center bolt hole in the axle pad.I think the actual measurement for the centerbolt is 2-3/4 to 3 inches from the axle centerline.always check it with the fenders in place. And remember, moving the axle back pulls the driveshaft spline out of the tranny, take care of that also.