Swivel ball is welded to axle housing. Fist measure current caster angle and decide what is your new caster angle. Then dissassemble everything you can from axle housing end. Just grind/cut out that welding. Swivel ball is piloted inside axle housing. Be careful and cut only thru axle housing. Then insert pipe thru trunnion bearing holes and measure casten angle. Then turn swivel ball to right position and measure caster angle. If ok weld it back.
Make sure that car is in desired height in first caster angle measurement. If you decide turn swivel balls for example 8° it is now easy to do because you know how much. No matter if axle housing is upside down. It is allways 8°
After all this work you might have some bump steer. And why? Because tie rod and panhard rod ought to be more or less parallel. Luckily panhard rod bracket is easy to modify.
Quite simple... isn't it?
