Interesting...so if you utilised the 255/35/19 from rear, effectively these could be fitted to front, and then a fresh (larger) set could be utilised for rear.
Seems too easy. :)
Also a 285/30/19 would be closer to stock for rear but unsure how it would fit.
A 255/35/19 on front would be a 1 inch wider tyre, than standard on rim. While a 285/30/19 would be a 1 inch wider tyre on rear rim.
Did the yanks not have larger rim widths on later models?
http://www.clublexus.com/forums/is-f-2008-2014/790087-255-35-19-and-275-35-19-michelin-pss-tire-set-up.html