[skidmarks]

As far as getting it centered. Put a piece of masking tape on the housing in the center. Measure the width from the backing plates and divide that in half and make a mark on the tape. Then measure off that to your springs. Make sure the springs are not twisted in or out. Double check your measurements from more then one spot like center to the springs inside and out and center to the outside of the frame rail. Tack the spring pads to the housing and check it all again. Then weld it up. Use common sense welding them on. Too much heat can cause it to warp