Autoblog and Yahoo may earn commission from links in this article.The 800-HP-Plus UpgradeWhen Ford specialist RTR Vehicles released the Spec 5 package for the Mustang last year, it was a bit of a shame that such a compelling package was limited to just 50 examples for the 2026 model year. After all, it delivered more power than the Mustang GTD at roughly half the price. But for those looking to boost their Mustangs with RTR, there's another option in the Spec 3 package.The RTR Spec 3's headline upgrade is a 3.0-liter Ford Performance Whipple supercharger that raises output to 810 horsepower and 615 lb-ft of torque – roughly 330 horsepower more than a standard Mustang GT. While it doesn't eclipse the Mustang GTD the way the Spec 5 does, the Spec 3 starts at $33,995, making it a significantly more attainable way to access supercar-level performance compared to the GTD's roughly $327,000 price tag.RTR VehiclesMore Than Just A SuperchargerThe supercharger upgrade is complemented by several other enhancements, including RTR grilles and a hood vent designed to improve airflow. Aerodynamic additions consist of a front chin splitter, undertray extension, rocker splitters, and a decklid spoiler, while the package also features 20-inch RTR wheels wrapped in Nitto NT555 G2 tires.AdvertisementAdvertisementMechanical upgrades are also included as standard, including adjustable front and rear sway bars, adjustable front struts, and adjustable rear shocks. These components allow drivers to tailor the suspension to their preferences, whether prioritizing ride comfort for daily driving or a stiffer setup for improved handling. RTR Vehicles says the Spec 3 was tested and validated by two-time Formula Drift champion Vaughn Gittin Jr., who also founded the tuning company.Meanwhile, optional upgrades include a leather interior, puddle lamps, pedal covers for Mustang models equipped with the 10-speed automatic transmission, an X-pipe exhaust, powder-coated wheels, and a Borla cat-back exhaust.RTR VehiclesOther Mustang Upgrade RoutesRTR Vehicles backs the package with a 3-year/36,000-mile warranty. For buyers who find the Spec 3's $33,995 starting price too steep, the tuner also offers the Spec 2 starting at $18,995, which includes the same styling and suspension enhancements but omits the supercharger.Buyers interested in a supercharger upgrade alone can turn to Roush Performance, which offers a package for the 2026 Mustang GT and Dark Horse starting at $10,399. The kit raises output to 810 horsepower and 630 lb-ft of torque.RTR VehiclesView the 3 images of this gallery on the original articleAdvertisementAdvertisementThis story was originally published by Autoblog on Jun 10, 2026, where it first appeared in the News section. Add Autoblog as a Preferred Source by clicking here.