While specific performance numbers varied slightly depending on options and condition, the Mustang GT's 5.0L V8 typically produced more horsepower and torque than the IROC-Z's 5.7L V8. The Mustang also often had a slight edge in acceleration times. The IROC-Z's higher displacement engine did provide some advantages in top speed in certain situations, but the overall performance favored the Mustang GT in most comparisons.
