The XR-400 was a fully operational concept car.  A "sporty" youth-oriented convertible  was built in 1962 by the Automotive Division of Budd Company, an independent body builder in Detroit, Michigan, for evaluation by the fourth largest U. S. automaker at the time, American Motors Corporation (AMC).

Origin

The objective of this car was to entice AMC to expand into a new market segment with a low-cost Rambler-based "sports convertible." The Budd Company was a long-time supplier of tooling, parts, and bodies to automakers. Budd also worked with Nash Motors, AMC's predecessor company, to develop the first monocoque (unitized) automobile body in 1940. By enticing AMC with this concept, Budd’s already existing business with AMC would increase. It planned to supply bodies and major sub-assemblies for the production version of this new car. Budd estimated that the new model could be available for public sale by October 1963, six months ahead of the Ford Mustang.

Design

The XR-400 was built on a shortened two-door 1962 Ambassador chassis. To keep costs down, Budd engineers kept front of the unit body with the engine and suspension in the same locations. The XR-400's long nose was accomplished by adding a second cowl section behind the original that made space for the battery. The car was styled by Budd with a rather clean and uncluttered body giving little indication of its Rambler sedan origin. A double crease in the beltline suggested a family relationship to the contemporary styling of Rambler’s large-sized cars.

The proposed model was a true 2+2 (two front bucket seats plus limited use seats for two back passengers) sleek, steel-blue convertible with a long hood and a short, stubby rear deck. The XR-400’s long 108-inch (2,743 mm) wheelbase and truncated overhangs gave it athletic proportions, while the top-up appearance suggested a close-coupled two-seater sports car. Classic sports car touches included a hood line that slopped lower than the front fenders, doors that had a dip in their top, and simulated scoops behind the front wheels.

Power for the XR-400 was supplied by a standard Ambassador 327 cu in (5.4 L) AMC V8 engine. The engine bay could accommodate any of AMC’s I6 or V8 engines. The transmission was an automatic (not typical of sports cars) controlled through a floor console mounted shift lever. Braking was provided by an experimental front disc brake system.

The interior used AMC’s front seats and many other hardware items. In classic sports car fashion, the driver had all controls and a full set of instruments (speedometer, tachometer, as well as gauges for fuel, water temperature, amperes, and oil pressure) that mounted directly ahead of a highly regarded three-spoke wood-rimmed Nardi (brand) steering wheel.

Budd's sales pitch to AMC included pioneering a market "presently untapped by any other manufacturer" with a car so "unlike anything else on the road it would attract widespread attention, provide your dealers with both a new profit area and morale-builder, and offer unusual advertising and sales promotion opportunities."

Expectations

The press release stated that the concept shows how modifying Rambler Ambassadors results in:

    "... A brand new type of car—one designed specifically to take over a healthy segment of the new car market presently untapped by any American manufacturer...."

Automotive press reports stated that such a new model could have appeared in AMC dealer showrooms, thus establishing a market segment at least six months before Ford's similar Mustang started the "pony car" market. Unfortunately, AMC turned down the idea. There were probably several reasons for this decision, including:

    * American Motors’ President George W. Romney, who cemented the company as a maker of compact cars, left the company in February 1962 to run for governor of Michigan.
    * His replacement, Roy Abernethy, began a strategy head-to-head competition with the Big Three automakers (General Motors, Ford, and Chrysler) across all major market segments.
    * The new model had very little interior room to compete successfully against other sporty compact cars such as the Chevrolet Corvair Monza and the Pontiac Tempest Le Mans.
    * American Motors was developing entirely new models for 1963 and this was a major capital drain. Entering a completely new market segment with an unproven car could be a costly mistake.
    * The company was itself working on a new compact fastback concept car called the Rambler Tarpon using the soon to be introduced third generation Rambler American platform.

Legacy

The Budd Company kept the only prototype model, but later renamed it "XR-Budd" and used it for marketing purposes. The prototype was upgraded with chrome-reverse rims, but the original version had full wheel covers. The car is now at The Henry Ford Museum.

There are two final ironies to the XR-400 story.

    * The idea was first presented to Ford Motor Company in 1961 when Budd developed a sporty convertible by combining a 1957 Thunderbird body with a 1961 Ford Falcon chassis. Ford turned them down (and subsequently based its new Mustang on the compact Falcon chassis) so Budd tried to pitch its concept to AMC.
    * In 1987 American Motors was acquired by Chrysler Corporation. At the time Chrysler was headed by Lee Iacocca, who, while working at Ford was responsible for introducing the Mustang. As Iacocca stated, "you either lead, follow, or get out of the way."

source: Wikipedia