"Bell (model 205) UH-1D (1963) had a longer fuselage than previous models, increased rotor diameter, increased range, and a more powerful Lycoming T53-L-11 1100 shp engine, with growth potential to the Lycoming T53-L-13 1400 shp engine. A distinguishing characteristic is the larger cargo doors, with twin cabin windows, on each side. The UH-1D, redesigned to carry up to 12 troops, with a crew of two, reached Vietnam in 1963. The UH-1D has a range of 293 miles (467km) and a speed of 127 mph (110 knots). UH-1Ds were build under license in Germany. UH-1D "Hueys" could be armed with M60D door guns, quad M60Cs on the M6 aircraft armament subsystem, 20mm cannon, 2.75 inch rocket launchers, 40mm grenade launcher in M5 helicopter chin-turret, and up to six NATO Standard AGM-22B (formerly SS-11B) wire-guided anti-tank missiles on the M11 or M22 guided missile launcher. The UH-1D could also be armed with M60D 7.62mm or M213 .50 Cal. pintle-mounted door guns on the M59 armament subsystem."
Source: http://www.fas.org/man/dod-101/sys/ac/uh-1.htm