Our alternators address the shortcomings of the failure prone stock 6G alternator found on 99-04 Mustang GT's. They feature a larger case for improved cooling and more efficient power production, and for many a better looking design. This alternator is built with quality parts, and is backed by a lifetime warranty!
Units come in standard aluminum cast. Powder coat finish options are available, see examples in the images.
Fits 99-04 4.6 Mustang GT's. This alternator has been installed with both Roush and Saleen supercharger systems and fits perfectly.
The Big 3 option is a wiring kit that replaces your factory power and ground cables with robust 0 gauge heavy duty, 100% copper welding cable. It also introduces a second ground cable and a fuse on the power cable. These cable kits are HIGHLY recommended as the stock wiring is only 10 gauge at it's smallest point which isn't even adequate for the stock alternator. Combine that with 20+ years of copper degredation and corrosion it's a recipe for disaster and an underperforming alternator. **Big 3 upgrade is REQUIRED on 250 amp units to retain warranty. If you don't purchase the wiring kit from us you will be required to provide proof of installation of a wiring upgrade on your vehicle in order for warranty to be approved.
***We build these alternators to order and usual build time is approximately 5 to 7 business days. If you need it faster than that, please let us know when you order and we will make every effort to accomodate you. We understand that people have race or show events they like to attend and we've been there. But, we have to know as early as possible in order to take action.
Reviews
We were having issues with our 2000 Mustang GT's electrical system. We bought the car from the dealership this year (2026), and it only had 64, XXX original miles. The one owner of the car before us left the car completely stock, only replacing the required things as necessary. We were in a pinch and needed a new, high-quality alternator. KMJ did not disappoint. They built us an alternator and had it turned around and shipped out within a couple of days. Definitely recommend KMJ for your needs!
Great product as usual, the amount of packing material used kept it safe and in good shape. Customer service and Ken assisting with any and all the questions I’ve had for a couple of my cars now has been great and I will continue to use Kmj for any alternators I may need in the future