Gran Turismo 7

After Menu Book 7 you unlock GT Auto, the second category inside GT Auto will let you customize the style of your car.
Aero parts are found in the Custom Parts option, and their availability depends on the car you are currently in. Most cars have at least a generic front splitter and generic rear wing.

This trophy unlocked for me when buying the type B rear wing for a 66 VW Beetle.

I believe this trophy is currently glitched. I bought numerous wings and side skirts and things and it hadn't unlocked. It finally unlocked when I bought a side skirt for a Chevrolet Camaro.