You may not have heard of Mil-Spec Automotive, but the company is starting to make a name for itself thanks to its restomod Hummer H1s, two of which recently visited Jay Leno’s Garage.

Mil-Spec Automotive is led by a trio of 23-year-olds who had a desire to bring the iconic H1 into the 21st century with modern technologies while still retaining the vehicle’s heritage that has made it a true American icon.

Also Read: Mil-Spec’s Overhauled Hummer H1 Gets 500 HP, $295k Price Tag

The two Hummers brought along by Mil-Spec included a four-door satin black example and a soft-top one that’s more suited towards desert driving. Both H1s feature Duramax 6.6-liter turbodiesel engines with 500 hp mated to Allison six-speed automatic transmissions. Other important mechanical components which distinguish the Mil-Spec models from typical Hummers include new aftermarket wheels and an onboard air system which powers the rear ARB Air Locker selectable differential while also providing air to pump up the tires and power various pneumatic tools.

Not only does the aforementioned 6.6-liter V8 deliver an impressive 500 hp and roughly 1000 lb-ft (1355 Nm) of torque, but it is also (relatively) fuel efficient, can run on biofuel and return up to 20 miles per gallon. Mil-Spec selected this engine not only because of its headline power and torque figures but also to help shift the negative stigma about H1s being extremely in-efficient gas guzzlers.

Those interested in Mil-Spec’s Hummer H1 can either let the company source and build up a vehicle, or supply them with an H1 who will they modify to the customer’s tastes.