I've had the K02's in a couple of sizes on my 4runner. I started off with the stock size with a load range c. I eventually put a lift on it and decided to trade them out for the 285/70r17 (which is a load range e). They have been great in both sizes. To be honest about it all, I have never took a terrible hit in the mpg department (even with the lift and 285's I'm still getting 17.5 mpg with mixed driving. I obviously am not a heavy footed kind of guy. These tires, in my opinion, do really well in the snow or ice for not being a dedicated winter tire. The one thing I will say about having a heavier tire/wheel combo (no matter how you get there) is that getting stopped is noticeable. In stock size, it wasn't even a concern, but now that I've got a larger 10 ply tire, I notice it has to work a little harder to get stopped (though it isn't terrible by any stretch of the imagination).
As a full disclaimer, I've been running some version of the BFG All Terrain for the last 15 years. There might be better tires out there, I really don't know. These tires have great traction, a good life, don't make a whole bunch of noise and I honestly can say I've never gotten a flat with them (yet I got 3 flats with the factory tires that came with my Tacoma before I swapped them out all within a month). With the 4runner, I drove to Discount the day after I bought it and replaced my brand new tires with the KO2's. I know this is a tire I can trust.