The 4.0-litre engine cranks out 368kW of power and 460Nm of torque in the GT3, but it will reportedly be retuned to deliver around 317kW (425hp) in the Spyder.
Even so, the car will prove a significant step up from the previous model, which utilised a 276kW 3.8-litre six-cylinder boxer engine.
The British magazine also says the Spyder will be fitted with a manual as standard, but a seven-speed dual-clutch transmission will be offered.
If true, a similar engine will likely be offered in the upcoming 718 Cayman GT4, which was last spied in November 2017.
Unlike that prototype, this Spyder test vehicle doesn't feature an overly aggressive front bumper design, although that may change on the final design.
Along the side we can see cross-drilled brakes with red calipers, and an enlarged air intake ahead of the rear wheels. At the back, there's a more prominent diffuser and two large exhaust tips.