on Autotrader you can not find one used 2007 GS 430 in the entire country.
Did they only make them for 2006?

 

The Lexus Website has a GS430 on it for 2007. So, I am guessing you could order one.

But really if you are going to buy a 2007 Lexus GS, why would you want a GS430 over a GS350?

So, not many have been sold. And if they were sold they would have to be up for sale again to appear on the used market.