On a 1995 Chevrolet 2500 truck, the brake light switch is typically located on the
brake pedal assembly. It's a small cylindrical switch, often mounted on or near the top of the brake pedal itself. You might need to look underneath the dash, above the brake pedal, to find it.
Because there are variations depending on the specific transmission and other options, it is advisable to consult a repair manual specific to your 1995 Chevy 2500 model. A diagram would greatly aid in its location. You can find these manuals online or at auto parts stores.