That's correct. Each side moves in 1.5" closer to the pumpkin. Are you going SOA? If so, do one side at a time. Use a welder's chalk to mark the centerline of the current pad before removing it. Set the new pad in place with axle stands or similar and a jack under the pinion to adjust the angle. Set it so the remaining spring pad is level, place the new one and spot weld it level then do the other.