The S197 Mustang GT already comes with the 5.0L Coyote V8, which is a strong foundation. The most effective performance upgrades depend on your goals (street, drag, or track), but popular options include:

• Cold Air Intake & Tune: Increases airflow and optimizes the ECU for better throttle response and horsepower gains (around +20–30 HP).
  
• Long-Tube Headers & Exhaust System: Improves exhaust flow, sound, and adds 15–25 HP.
  
• 
  Forced Induction (Supercharger or Turbo Kit): Adds major power — 150+ HP gains possible with proper supporting mods.
  
• Suspension Upgrades: Lowering springs, coilovers, and upgraded sway bars improve handling dramatically.
  
• Rear Differential Gears: Upgrading to 3.73 or 4.10 gears improves acceleration but sacrifices a bit of top speed.

The S197 Mustang GT’s stock Coyote engine is impressively durable.

• Stock internals can reliably handle up to ~700 HP with a good tune and supporting fuel system.
  
• For forced induction builds (supercharged/turbocharged), staying around 600–650 HP is recommended for daily reliability.
  
• Above that level, consider forged pistons, rods, and crankshaft to prevent catastrophic engine failure.
  
  Proper tuning and fuel delivery (injectors, pump) are essential to safely reach these limits.

The S197 chassis is stiff, affordable, and well-supported in the aftermarket. It bridges old-school V8 character with modern technology—offering solid rear axles (2010–2014) or independent rear suspension (2015+, not S197), good weight distribution, and a strong 5.0L engine.

• Lowering springs or coilovers (Eibach, BC Racing, KW)
  
• Sway bars (front & rear adjustable)
  
• Control arms and panhard bar to reduce axle movement
  
• Strut tower brace and subframe connectors for stiffness
  
• Performance tires (Michelin PS4S, Nitto NT555 G2, etc.)
  

For track use, coilovers and adjustable dampers make a huge difference.