If you are keeping the rake relatively the same, you will not have to recalibrate at all. I lifted the front only on both my LC and 4R and did not do any recalibration. There is a window of range for if you were to tow a trailer or have a large load in your cargo area, the rear would naturally...
General Tire Grabber aTx come in C rating for 275/70/18. In addition, they will rub on your front mud guards unless you install the oem mud guards from a TRD Pro or Trailhunter. These are only 1' wider but have a flush fit against wheel well.