That size will present some clearance issues (fixable) but also likely not roll if you are reduced to bump stops.
You'd also need to find a solution for a full-size spare (won't fit underneath)

For your described use, I would suggest at most 265/65 to avoid the above issues.
E load rating can be found in that size, or you can also use XL rating (opening up more options)

I have "smaller" XL 265/60 (still bigger than OEM) and have zero negative side effects during use, and my matching spare fits easily underneath
my occasional off-roading is sure-footed (A/T tire with snowflake)

Depends how much you WANT the larger size.

 

^ Spot on advice.

To recap, I run 275/65/18 which is actually just a hair past the limit on max size. 32.1" by 10.8". The fronts are not an issue at all, not even remotely so. The rears have slight rubbing but I did not have to relocate the rear coolant lines to the heater - these can be an issue if you have rear HVAC setup as the pipes run being the rear wheel well liner. I did heat my liner with a heat gun to melt and mould it away from the tire in a couple spots, mainly my rear coolant lines. Now with a few thousand miles on them, there is some more apparent rubbing but it is of no concern. If I were to go with an event taller tire, I would have to get strut spacers to reduce tucking of the tires. I am trying to stay away from those spacers since they reduce articulation a bit. I will add that my suspension, less the struts, is very new OEM with a very good alignment. Old suspension will result in more play and difficulty aligning properly. If suspension bushings are worn then you will have a much greater chance of rubbing when pushing the limits on size.
Also mine are e-rated. I highly recommend looking at Toyo Open Country AT3s. When I was looking they came up as the best over and over. Great A/T tire and not noisy or such. I am happy with how my Bridgestones perform... but with the cracking, never again will I buy them or recommend.

 

It turns out the propeller sound coming from rear of our LR3SE were from the worn rear hubs.So the front bearings and the rear failed while using the slightly larger than orm Hankook AT Dyna All Terrain tires.
When we first put those tires on 37000 miles ago I felt that they put more resistance or strain on the rolling affair. Now back to oem size Bridgestone Alezia Tires and replacedbearings in rear the car is back to being smooth again.The AT tires sure looked good but lasted only 37k and these Bridgestone look good too.

 

Hi..for highway driving mostly ?

 

Yes mostly highway
some off-road
some towing

they ended up lasting just over 60k
i replaced them with 265/65 cooper rugged trek also XL

i do notice a decrease in fuel economy
and slightly more road noise which I actually like
but the trade off is a larger more aggressive looking tire

i hope they last as long

i still say the 265/60 wild peaks are probably the right choice for looks, quiet, economy, and longevity for occasional offroad

 

But the 255/60 18 is the standard size for LR3.
Anyway just ordered a set of Continental on the recommendation of the Tire Rack guy.
I was looking for the Hancook as those lasted well for us in the LR3 in the past but no longer made.
In the past the Firestone Destination had best lifespan but those were discontinued in this size long ago.The Bridgestone Alenza AS Ultra had the shortest lifespan for us ever.After using them for a month I thought to my self wow they look like these are wearing fast..less than 30,000 miles Bridgestone finished and they come with an 80,000 mile "warranty"..what a joke.
Wife wanted the bulky big teeth AT type but very few in this size.
I hope Continental lasts

 

There are many advantages to ditching the stock 255/60 size and going to 265/60 (and virtually no downsides)

so many more options
lower prices
more comfortable ride with taller sidewall
matching spare still fits underneath

just make sure you keep XL load rating
hope the continentals treat you well
consider 265 next time .. there are many forums users who can confirm
doubt the tire rack guy has any clue about our trucks except what OEM size was