The lower radiator hose on a 1988 Ford Bronco's engine block connects to the
engine block's water outlet fitting at the bottom of the engine. The exact location varies slightly depending on the engine (302 V8, 351 V8, etc.), but it's always at the lowest point of the engine's cooling system to allow coolant to drain back into the radiator.
You'll likely find it near the bottom of the engine, possibly somewhat toward the front. To be certain, you'll need to consult a repair manual specific to your Bronco's engine. A visual inspection under the vehicle, after locating the radiator and following the lower hose, will be the most direct method.
