This 1951 Jeepster is owned by club members Wendell & Sandi Olson was most likely a 1950 manufactured unit, sold and titled in 1951. It is designated as VJ-3 463 as it had the F134 Hurricane F-Head engine, producing 72 bhp at 4,000 rpm, used in 50 and 51. This engine provided power to the rear end through a three speed manual transmission with overdrive.

General background:

After World War II, Jeep trademark owner, Willys, believed that the market for the military-type Jeep would be limited to farmers and foresters, therefore they began producing the "CJ" (or Civilian Jeep). Willys then began producing a new Jeep Wagon in 1946, and the Jeep Truck in 1947.

Then, Willys developed the Jeepster to crossover from their "utilitarian" type truck vehicles, to the passenger automobile market. In the process, they developed "one of America's most daring postwar automobile designs."

Willys-Overland lacked the machinery to form deep-drawn fenders or complicated shapes, so the vehicle had to use a simple and slab-sided design. Industrial designer Brooks Stevens styled a line of postwar vehicles for Willys using a common platform that included the Jeep pickup and station wagon, as well as a sporty two-door open car that he envisioned as a sports car for veterans of World War II.

The Willys-Overland Jeepster ("VJ" internally) was introduced in April 1948, and produced through 1950. Some leftover models were sold in the 1951 model year.

1948:

The 1948 VJ-2 Jeepster included numerous deluxe features and interior fittings. These included, whitewall tires, hubcaps with bright trim rings, sun visors, deluxe steering wheel, wind wings, locking glove box, cigar lighter, and a continental tire with a fabric cover. Fittings and interior were also deluxe, there were chrome step plates on the rear fenders, instruments included a speedometer plus gauges for monitoring amps, oil pressure, water temperature, and fuel level. Door panels and interior kick panels were finished in a leather-grain Masonite, and floors were covered with a rubber mat and colorful piping ran around the edges of the seats. The Jeepster's front end sported a bright T-shaped grille bar plus a chrome bumper with overriders. Most Jeepsters came with two-tone paint, with the secondary color (generally black) edged by a thin chrome strip that began at the cowl, ran along the upper body and doors, and wrapped around the back. (Even Jeepsters without the two-tone paint came with this molding.)

Popular options included a radio and heater. Only 10,326 of the 1948 Jeepsters were produced and many of them remained unsold when the 1949 models debuted. Apparently, the unsold Jeepsters were retitled as 1949 models.

The VJ-2 Jeepster was powered by the 62 hp Go Devil engine, a 134 cu in L-head straight-4 also used in the CJ. A 3-speed manual transmission with overdrive was used, with drum brakes all around. The vehicle's front end and single transverse leaf spring suspension, was from the Willys Station Wagon, as was the rear driveline. The flat-topped rear fenders were copied from the Jeep truck line, as were the pair of longitudinal rear leaf springs. The Jeepster had plastic side curtains and was priced at $1,765.

1949:

The 1949 Jeepster began production with a one-model/one-engine offering. The price was lowered to $1,495, with some previously standard features were returning as extra-cost options. Toward the middle of the year, an additional model was introduced, the VJ3-6, powered by a new six-cylinder engine. Production for the year totaled only 2,960 units. Of these, 2,307 were equipped with the four-cylinder engine and 653 with the new six.

1950:

The VJ-3 Jeepster had very little standard equipment. This time there were two engines offered, changing the Jeepster's designations to VJ-3 4-63 for the four-cylinder and VJ-3 6-63 for the Lightning-equipped six-cylinder.

The 1950 model year saw the first styling revisions that included a redesigned front end featuring a V-shaped grille with horizontal chrome trim, and a new dashboard. New engines and designations dependent on what part of the year it was. Early 1950s four-cylinder Jeepsters were VJ-3 463, and the straight-six Jeepsters were VJ-3 663. The later-year Jeepsters were VJ-473 and VJ-673, respectively. Production was 5,845 units, of which 4,066 were four-cylinder models and 1,779 were sixes.

1951:

The 1951 Willys Jeepster looked very familiar. After poor sales in 1950, the decision was made to end Jeepster production, but Willys, stuck with a number of unsold Jeepsters, decided to retitle the leftovers. Thus there would be a line of 1951 Jeepsters, at least in name.
Engines:

1948-1950 L134 Go Devil 134.1 cid

1949-1950 L148 Lightning 148.5 cid

1950 F134 Hurricane 134.2 cid

1950 L161 Lightning 161 cid

For some really good additional information click on the link below:

http://auto.howstuffworks.com/1948-1951-willys-jeepster.htm