A separate US Marine Corps variant, the shorter two-seat M1163 prime mover is combined with the M327 towed 120 mm heavy mortar, and also became its ammunition hauler after the M1162 trailer was cancelled.

[3][4][5] Two different versions of the Growler were developed; the M1161 light strike vehicle (LSV), and the M1163 prime mover variant as part of the Expeditionary Fire Support System (EFSS) towed heavy 120 mm mortar.

A number of the separate 36-round ammunition trailers, the M1162, were ordered but further design was dropped and its duties to carry the 35 lb mortar shells were incorporated into the M1163 Prime Mover.

The Growler's central role of cross-country scout and aerially-deployed forward unit has led to further modifications, including use of the rifled precision extended range munition (PERM) system.

The GUSS system's aim is to lighten troops' loads by carrying up to 1,600 lb (730 kg) of equipment; it can also serve as an unmanned medical evacuation vehicle.

[11] In June 2012, the United States Special Operations Command (USSOCOM) expressed interest in procuring Non Developmental Item (NDI) vehicles that would be highly mobile, V-22 transportable platforms.

A limited objective experiment and technical assessment was conducted by the Marine Corps Warfighting Laboratory in September 2015 to define the need and find vehicles to fill it,[9] performing missions ranging from light strike to logistics and casualty evacuation.

[9] Manufactured between 2004 and 2010, Growler ITV procurement and fielding was ineffectively timed since operations in Iraq and Afghanistan led to most units relying on armored vehicles because of the threat of roadside bombs.

Although designed for light strike, experiments have shown an ITV's greatest roles to be casualty evacuation (CASEVAC) and logistics to lighten individuals' loads.