Loosely bolt the spring into the spring hanger.
Measure and mark out 900mm from the rear of the chassis forward. Using a square, position the spring, so the spring centre bolt lines up with the mark.
Adjust the spring so that the outside edge of the spring is flush with the chassis rail along the length of the spring.
Double check the position of the spring and tack weld the spring hanger to the chassis.
Slide the slipper onto the other end of the spring and centralise over the spring tail to allow movement of the spring when loaded, and enough to prevent the spring from falling out.
Weld spring hangers and slippers to the chassis once happy with their position.