It seems no one can give a clear answer for you...i found this post of someone who has a 235/35/20 setup and he slightly modified the inner fender....
https://www.clublexus.com/forums/sho...81&postcount=4

 

the only way you'll need a spacer is if your front wheel wont clear the caliper. as i said before, for the rear you can run that tire size but your offset should probably be at least +40 or higher. you should be able to run the 235/35/20 without a problem after modding the fender liner. but i still suggest running a 245/30/20 instead... the next time i purchase 20" wheels and tires for my 250 i plan to go with 245/30 and 275/30. what wheels are you looking to use? if you have a 350 i suggest finding a reputable vendor such as D2 or tirerack to make sure the wheels you pick will clear the caliper.

 

D2 are a bunch of cool guys. I have talked to I believe shawn and he has been helping me. I am considering going with Maya STM in black or Sportecs if they will fit. I am not sure if they have a lexus fitment or not. They started with just Porsche, Audi, and VW I have seen them recently on bimmers and Benzos though so I imagine there would be a fitment for our cars. If you go to Mayawheels.com there are links for both Maya wheels and Sportechnic which is a sportec wheel with a slightly different name.