Complex sentence: The M3 was also adapted as a main gun for various armored vehicles, starting with the experimental T7 which was accepted as the 90 mm M3, used on the M36 Jackson anti-tank vehicle, and the M26 Pershing heavy tank.
Split into simpler sentences: The M3 was also adapted as a main gun for various armored vehicles, starting with the experimental T7 which was accepted as the 90 mm M3. Nevertheless the gun was used on the M36 Jackson anti-tank vehicle, and the M26 Pershing heavy tank.