Many upgrade to that size on 100% stock 4Runners with no issues. The BFG K/O has been reported to rub lightly. All other including the Nitto are fine. Many use the Nitto and like the tire. In addition to the improved aesthetics of a slightly bigger tire the 265/70 is often times a bit cheaper than the 265/65.
The 'downside' is most report a .5-1.0mpg decrease when compared to an all-season in the OE size.
If you choose to buy 5 the 265/70 will fit in the spare tire location. If you choose to keep a 265/65 it will work fine as a spare. The 4wd/awd system on the 4Runner will tolerate a slightly difference in size for short periods of time. I wouldn't want to change to the spare in Richmond and drive 75mph to Daytona but a couple of days of normal driving is fine.
Good luck!
:cheers: