It will be no problem whatsoever.
Go onto tirerack and compare some tire dimensions for 265/65x18, which is both wider, and taller than you're wanting to try. This size fits fine on stock lr4.
For example, 265/55x20 is about the same diameter, but still wider, than 255/55x20. So, the tight spot usually a concern, at the top of the tire behind it, the upper control arm or A arm comes close to the tire. I think you'd still be able to slide your hand through on that size you want to use.
The other tight spots when turning, should also be just fine because other people are using wider tires pushing the limits. You won't be pushing the limit and will have no worries.
In fact, when I first started out I had 20" wheels from a supercharged model which were 9" wide and just barely fit a 285/50x20 with slight rub when suspension dropped too far (rub was only on that upper control arm bit behind the top of tire that you can't quite see). 275/50x20 fit perfectly though and it's wider than what you're planning.
The size you want will look good and give you a bit of extra sidewall for rougher roads and nicer ride. Good idea!