The tire is smaller than stock, and smaller than 275/55/20. Lot's of useful stuff here, worth a long read:
http://www.toyota-4runner.org/5th-g...r-5th-gen-tire-fitment-guide.html#post1550444
Still may rub if you get the offset/backspacing wrong, but I can't help you with that math. Downside is less sidewall, but that's not as big an issue for highway driving. Those tires probably would not be recommended off road.
I'm at about 95% highway driving which is why I'd like to opt for the 285/50 R20 size... The chart is great info! Looks like the tire I want is in the Yellow. What kind of fender liner mod is typical? I was hoping the 9" wheel width would avoid any mod...