There is no need for stiffer springs.
There is an adjuster plug on the end of the joint. As the plug is tightened down, the spring is compressed, and the spring gets "stiffer". When the adjuster is tightened fully, then the joint becomes solid, no play.
FJ40Jim,
Can you explain the difference with the 80 series steering a bit more in detail? They have no springs at all? Are there any good links that explain these differences and the conversion? Thanks.