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Bit of a trick question, so no simple answer except stock tire size.
Front wheels are the trick part, because they turn left and right, so while you can put on larger tires because body is now higher up, they can rub frame/parts when turning.
This is is avoided by changing the "offset" of the wheels.
read on offset here: The Ranger Station wheel guide - Everything you need to know!
and here on tire diameters: Ford Ranger / Bronco II Tire Fitment