Hi fellow Lexuns
This is another tip for you I have learned in the ten years of ls400 ownership,
The Workshop Manual will show. for replacement of front upper control arm both sides ,complete removal of suspension including shock and spring. It is possible to replace arm without doing this.Jack up the car so the side you are working on is hanging to its full extension of the spring,remove the top ball joint pin and nut and loosen that connection ,then loosen off the three nuts in the engine bay( do not take them off completely) that hold the top end of the suspension to the body .
This will allow enough movement to get the bolts out that hold the control arm to the body you may have to bar the spring up or down a tweak but we changed the upper control arms in less than an hour per side without messing about with lower suspension components.I can only vouch for the mark 1 for this short cut .