* Condition of the vehicle: Worn components, tire pressure, and overall maintenance will affect performance.
* Gear ratios: The specific gearing in the differential will influence top speed.
* Aerodynamics: Even minor modifications can impact top speed.
* Elevation and weather conditions: Headwinds and altitude will reduce speed.
While it *might* be able to reach slightly higher speeds under ideal conditions, 75-80 mph is a reasonable estimate for the practical top speed of a stock 1988 Bronco II 2.9L 4x4. It's important to remember that exceeding the vehicle's recommended speeds is unsafe.