More developments resulted in M3A3, the final version. This type had a welded hull and the position of the driver was moved forward and somewhat higher. It could also take more ammunition and fuel on board. The turret was enlarged and therefor the radio could move to the back of the turret. The M3 models before the M3A3 had pistol ports, these were deleted in the new turret. Of the M3A3 were 3427 built, and the British army received 2045 of them. The M3A3 was almost exclusively produced for the Lend-Lease and served, besides the British, with the Commonwealth, Soviet Union and the Chinese. The American army only used a handful.

Because the gun proved too light in action against enemy tanks, the turret was sometimes removed altogether, so it could be used for a fast troop vehicle (Kangaroo), ambulance or, with extra communication apparatus, as a commander vehicle.

A proposal of Cadillac, a unit of the GMC group, to give an M3 a double Cadillac V8 engine was accepted in 1941 by the Ordnance Department. A standard M3 was converted to accept the 'Twin'Cadillac and a commercial used transmission was built into the vehicle. To take away any doubt, if there was any with the Ordnance Department, the M3E2 made a 500 mile trouble free testdrive between Detroit and Aberdeen at a speed of 50 miles an hour.

A new light tank was born and went into production. First as 'Light Tank M4', but it was changed in Light Tank M5 (the British Stuart VI) to counter the confusion with the Medium Tank M4 (Sherman).
The back of the M5 was raised to house the Cadillac engines. Also the upgraded M3A3 (Stuart Mk V) was used to develop the M5, which led to the M5A1 in September, 1942. Both tanks had a sloping hull at the front with enlarged hatches for the driver and co-driver. A better watertight sealing was improved and on the back of the turret was room created for the radio.

Early 1943 the M5A1 took the production line in favor of the M5. Around 7000 were built of the M5 versions. They served until the end of the Second World War when the M24 Chaffee Light Tank appeared in 1944 in Europe.

The M5 was always on the frontline with reconnaissance units. It was a agile vehicle and with her speed of 45 miles an hour and her firepower it gave good support to the up-front recce teams. The firepower and armor was inadequate against German panzer, but against enemy infantry and light vehicles it was a great little tank.

An important version of the M5A1 was the M8 Howitser Motor Carriage. It had a 75mm howitzer in an open turret. In 1944-45 they operated in conjunction with Medium Tank Battalions of Headquarter Companies to give extra support

First thing that may be noticed on this version, is the short barrel of the howitzer is covered with a wide muzzle break, which protrudes in front over the barrel. There was room for 46 shells. The elevation of the howitzer ran from -20 to +40 degrees. The driver and the assistant driver, who both had an steering mechanism, had no hatches to enter, or escape, the vehicle, but entered it though the turret. In the turret, which was open at the top, the gunner and the loader had their positions. The assistant driver had no machinegun in front of him. Because as it function as an howitzer, it was not in direct position at the front, but a short distance at the rear. The only protection was the .50 machinegun at the rear of the turret.

Far into 1944 the M8 was used in this howitzer role, before the M4 105mm Sherman tanks took it over. Testing was done with a 75mm gun in the M8, but the lack of room to stow ammunition, and the thin armor withheld the production of this version.

In the World there are still a lot of M3, M5 Light Tanks and M8 Howitzer Motor Carriages to be found, and some of them are restored back to factory fresh and drive around during manifestations. In Normandy are some remarkable types to be found, such as the M3A3 in Ouistreham at the Musée Le Grand Bunker and a recovered M5A1 in the museum with wrecks from the bottom of the sea of Normandy, which can be visited near Port-en-Bessin (see picture higher on this page). Another M5 can be found at the 'Dead Man's Corner' at Ste-Côme-du-Mont.

In Holland there are also a couple of Stuarts to be found. During remembrance days, such as the liberation of Holland or ‘Market-Garden’, these tanks are shown to the public. And also during meetings of owners of these vehicles, such as the Dutch organization 'Keep Them Rolling'.