Pair of adjustable tie rods.
When you change the length of the lower control arm to attain the desired degree of camber, the caster also changes. To reset it you must ba able to change the length of the tie-rods.
These special adjustable tie rods are almost twice the diameter of the stock version and are far less likely to bend.
Remember that in addition to controlling caster, these tie rods also control stability under braking. This brand have a hexagonal cut on the rod for easy adjustment.
Do not use harder bushes on both sides, as no advantage is gained. Hard on the outside and soft on the inside. Use kit C-STR627.