these BJ Jeeps are the Second generation (1950–1959) including in it the 20 series...according to this:
1950 - The Korean War created demand for a military light utility vehicle. The war put a Jeep on Japan's doorstep. The United States government ordered 100 vehicles with the new Willys specs and Toyota was asked to build them.
1951 - The Toyota Jeep BJ prototype was born in January 1951. This came from the demand for military-type utility vehicles, much like the British Land Rover Series 1 that appeared in 1948. The Jeep BJ was larger than the original U.S. Jeep and more powerful thanks to its Type B 3.4-liter six-cylinder OHV Gasoline engine generated 85 hp at 3600 rpm and 215 Nm torque at 1600 rpm. It had a part-time four-wheel drive system like the Jeep. Unlike the Jeep, however, the Jeep BJ had no low-range transfer case.
1951 - In July 1951, Toyota's test driver Ichiro Taira drove the next generation of the Jeep BJ prototype up to the sixth stage of Mt. Fuji, the first vehicle to climb that high. The test was overseen by the National Police Agency (NPA). Impressed by this feat, the NPA quickly placed an order for 289 of these offroad vehicles, making the Jeep BJ their official patrol car.
1953 - Regular production of the Jeep BJ began at Toyota Honsya Plant (Rolling chassis assembly), and body assembly and painting was done at Arakawa Bankin Kogyo KK, later known as ARACO (now an affiliate of Toyota Auto Body Co.).
1954 - The name "Land Cruiser" was created by the technical director Hanji Umehara. "In England we had another competitor - Land Rover. I had to come up with a name for our car that would not sound less dignified than those of our competitors. That is why I decided to call it 'Land Cruiser'," he recalls.
1955 - The original 85 hp Type B gasoline engine was replaced with a 125 hp, 3.9-liter Type F gasoline engine (additional).
1955 - The 20 Series was introduced alongside the BJ-T (Touring), BJ-R ( Radio ), BJ-J (Cowl-chassis for a fire-engine with Type B gasoline engine), and FJ-J (Cowl-chassis for a fire-engine with Type F gasoline engine). It was designed to have more civilian appeal than the BJ for export reasons. It also had more stylish bodywork and a better ride thanks to longer four-plate leaf springs which had been adapted from the Toyota Light Truck. Under the hood it sported a more powerful 3.9-liter six-cylinder Type F gasoline engine. The interior of the vehicles were made more comfortable by moving the engine 120 mm forward. The 20 Series still had no low range but it had synchromesh on the third and fourth gears.
1958 - The first Station wagon Land Cruiser was introduced with an even longer 2650 mm wheelbase (the FJ35V; wagon and van). The FJ-25 production started in Brazil being the first Toyota vehicle built outside Japan.
1959 - The first Toyota vehicles were exported to Australia initially for use in mines, dam construction spot, and snowy areas.
http://en.wikipedia.org/wiki/Toyota_Land_Cruiser