What is the correct battery size for the 2016 Toyota 4Runner?

There isn't a correct battery, per se, for Your 2016 Toyota 4Runner. That is, You pretty much can use whatever CCA and brand Your budget allows. The Group size is going to be 24F, but there are deviations here, from MT-24F to MTP-24F to MATX24F. All of these will fit in the V6 and 4.0 liter engines interchangeably, and the difference with them is that the cold cranking amps run froM600 in the MT to 750 in the MTP. Now, You may also consider that the AGM batteries (absorbent glass mat), while more expensive, last longer with less maintenance. For a brand, check out the Optima RedTop, which consistently wins awards for best overall value, year after year.