Divide the chassis length in half and mark the chassis rails, then accurately measure where you want the spring centers to be - ideally between 2" to 6" behind the center of the chassis and a good compromise for general cartage is midway at 3"behind the center. Double check your measurements.
Find the center of the chassis and mark an offset behind the center around 3" and fit the center of the rocker assembly.
Set up your suspension rocker so the main rocker bolt center is lined up with the suspension offset you have marked and clamp in position. Set up the front spring in its hanger and fit to the rocker unit.
Adjust the spring so that the tail of the spring can move freely when the rocker oscillates without binding or dropping out.
Operate the rocker and check that the spring has clearance. Adjust the springs to prevent binding or dropping out of the rocker unit.
Bolt the rear spring into the rocker unit.
Set up the springs and rocker assembly and align them to the outside edge of the chassis rails
Make sure that the outside spring edges are flush with the outside edge of the chassis rail and once double checked, tack weld the spring hanger and suspension rocker to the chassis rail.
Once this is completed on both sides, position the slippers over the spring tails allowing for clearance between the spring and the slipper for the spring to move in and out when loaded.
Again make sure the outside edge of the spring is flush with the outside edge of the chassis and tack weld the slipper in place.
Where the spring components are unsupported fully along the chassis rails, you will need to cut a couple of packers to support the overhang of these parts and weld into position.
Where there is no support under the rocker assembly and spring slippers, cut and fit packers to suit
Once all components are in position, remove the springs and fully weld around the hanger, rocker, slipper and packers.