Start with what the Ford GPA is: a car with 4-cyl. side valves, built from 1942 to 1943, in a decade split by war, when civilian production stopped and restarted. What it meant takes a little longer.
Where it came from
The Ford GPA "Seep" (Government 'P' Amphibious, where 'P' stood for its 80-inch wheelbase), with supply catalog number G504, was an amphibious version of the World War II Ford GPW jeep. Over 12,000 were made, serving with Allied forces in World War II, from D-day onwards, throughout Europe and the Pacific theatres. After the war as surplus they found many niche roles, and today examples can be found in museums collections or at military history shows.
Design features concept was similar to the larger and successful DUKW amphibious 21⁄2-ton truck were used on the GPA, but unlike these and the jeep, the 'seep' was not as successful a design. It was considered too slow and heavy on land, and lacked sufficient seagoing abilities in open water, due mainly to its low freeboard. Despite this it did have widespread use across the theatres of WW2. The Soviet Union received one third of the total GPA production under Lend Lease, and were sufficiently satisfied with its ability to cross calmer inland waters, that they produced their own influenced variant GAZ-46 based on operations and feedback with the Ford GPA.
Under the skin
The engine is 4-cyl. side valves; other versions carried different engines, listed in the specification table below. On the scales it comes to 1110 kg. Drive goes through a 3-speed + 2-speed transfer case / Low range engages FWD / Power take-off / PTO propeller drive. The wheelbase is 84 inch. These are manufacturer figures carried by Wikipedia and Wikidata, not road-test measurements.
In context
In the Ford line-up the Ford GPA has a clear place: the factory was United States. The cars a buyer would have weighed it against include the Lincoln Continental, the Alfa Romeo 430, the Dodge WC-54. Nearby in the Ford catalogue sit the Ford 021C and the Ford Escort.
Owning one today
MotorJury scores cars on the United States complaint and recall record, and the Ford GPA has none: too old, too rare, or never sold there. Its value today is a collector's question, decided by provenance and condition rather than by a class average.