Hi Erik,
As I previously suggested the photographs confirm the oil leak is coming from the valve cover(s) gaskets which have failed.
If you have some basic tools I also provided a link on how to DIY the job yourself.
The parts you need are available from Rockauto.com
https://www.rockauto.com/en/catalog/lexus,1996,ls400,4.0l+v8,1187513,engine,valve+cover+gasket,10710