Ken (BoostedInline6) once told me the easiest way to see if a truck/4Runner came with 31 inch tires was to see if it has chrome wheel well trim.

He was saying this in reference to see if the truck had 4.56 gears, but I would think this would still apply in this case.

My Truck: 1987 XtraCab DLX 22R 4WD 5 Speed Manual
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"Speed has never killed anyone. Suddenly becoming stationary, that's what gets you." -Jeremy Clarkson