Hi Sbelangia,nice to see something different on here,your car looks very eye catching mate...fairplay for choosing them wheels,bet there a pig to clean though...
What offset are the 20 inch wheels,the Ls 400 has a wheel offset different to most cars,its 50mm standard offset so you need to buy as near to the 50mm offset so they dont rub.I had problems with putting 18 inch wheels on my car,they rubbed on the front.I had to have the wheels machined,there fine now...
As for the ride height of your car,coilovers is the way to go,there not cheap but you can adjust the stiffness and ride height of them...
The ones i was looking at were made by "Tein"....but there £1200 here in the uk!!!
Good luck,let us know how you get on ;)
theres the Tein link for you,if thats of any help
http://www.tein.com/