Now here's how the XT-Bird became the XR-400. Despite Ford's rejection, Budd Company evidently felt the XT-Bird concept attractive enough to interest someone else. We say "evidently," for the very next year, 1962, Budd pitched American Motors the exact same idea with an all-new prototype dubbed "XR-400" -- "R" for "Rambler," of course.
Proposing the XR-400 to AMC made even more sense for Budd than plying the XT-Bird at Ford. At the time, as a later Budd press release noted, the firm supplied a great deal of AMC's tooling, plus numerous body stampings, structural parts, and sub-assemblies.
More important to this story, Budd and AMC had collaborated on the one-piece "Uniside" rocker/pillar/door frame assemblies destined for AMC's new 1963 Rambler Classic and Ambassador. Budd also viewed XR-400 as a showcase for all its many capabilities.
As Thomas J. Ault, president and general manager of the firm's Automotive Division, later recalled: "We had a dual purpose in mind. The first was to the industry that we could take a standard production-model car and, by rearranging high-volume structural parts, create unique assemblies -- and produce completely new vehicles with a minimum of new panels and modifications. We did [XR-400] at relatively low cost for development and new tooling, and in very short time.
"Secondly we wanted to demonstrate that Budd Automotive is one of the few, if not the only supplier capable of taking on complete programs. We can start with a designer's sketch, do the designing, engineering, prototypes, testing, and perform every other step necessary to mass-produce completely assembled automobile bodies."
Naturally, Budd hoped to make big money from AMC by supplying the "unique assemblies" for its proposed "sports convertible," besides doing all the up-front work.
What Budd offered AMC was an open 2 + 2 "sports car," à la XT-Bird, derived from the two-door sedan version of the new 112-inch-wheelbase 1963 Classic/Ambassador. Because those cars weren't yet in production, the XR-400 prototype was built from a two-door 1962 Ambassador with 108-inch wheelbase and 327 V-8, though it assumed use of the approved 1963 Uniside design.
Specifically, Budd planned to clip production Unisides at the B-posts above the belt, at the sills just behind the B-posts, and at the A-pillars about 7/8ths of the way up. The result was a still very rigid structure with integral cowl, stub B-posts, and lower-profile windshield frame.
So modified, this assembly would be shoved rearward exactly 16.24 inches from its stock 1963 position to accommodate the long-hood styling deemed essential for a sports car. Rear chassis rails were also trimmed -- by no less than 14.3 inches -- to suit what Budd called a "stubby rear similar to many European sports cars."
No major change was envisioned for the 1963 Classic/Ambassador chassis, a conventional box-section affair with integral floorpan. This was because each Uniside comprised inner and outer stampings welded to the rocker rails, which made the rearward "slide" easy to achieve on an assembly line.
That was just as well, for numerous changes were required elsewhere. Besides mostly new exterior sheetmetal, the XR-400's unique styling meant a heavily modified AMC driveline: engine lowered by two inches; radiator lowered by 3.5 inches; shortened fan blades and oil-filler neck; resited air cleaner, battery, and heater; reshaped exhaust system; and new rear engine mount, pedal box, and gas tank.
The car's format also dictated a plethora of new underbody components including the top well, rear-seat structure, and fender-wells, plus revised front suspension and dash mounts, reinforced and relocated front-seat anchorages, reshaped fuel-filler housing, and different inner panels for doors, hood, and trunklid.
Check out the next section to learn how Budd Company attempted to sell their idea to AMC.