LPG has been discussed before, but it's an awkward one to search for as "LPG" is too short for the search system to use!
Ensure you get a Flashlube system fitted, this will lubricate the valves in the same way that conventional fuel does. This is pretty-much essential for all Toyota and Lexus engines. Search for Flashlube on eBay, you'll find it.
As far as I can tell it's the same engine as the RX300 (3 litre V6), but that's just from searching the net - not under the bonnet!