Chrysler 300's were no exception. There is one notation in the AMA specs stating that the 1957 Chrysler 300C's optional 390 hp engine sported Holley carburetors, but  it is unlikely that any 300s were released to the public with Holley carburetors. Even Holley's master list of every application ever used does not show this application.  

The Automobile Manufacturers Association Consolidated Specification Questionnaire, in which 300C specifications are provided, lists in the Engine and  Fuel System section that the brand of carburetor is Carter.  Chrysler filled out these forms and included a footnote stating "Optional Holley."  The note is retained through the first and second (final) AMA sheet revisions. 

This optional availability is also noted in the Ross Roy Data Book "Models, Colors, Trim and Equipment" section on page F-21. Additionally, in factory technical report #4406.522 an optional intake manifold #1828027 is shown.

Throughout the AMA form when the word "optional" was used regarding engine equipment, it referred to the optional engine: the 399 code, 390 horsepower version.  So we expect this footnote to mean that Holley carburetors came on the 390 HP optional motor.

However, Holley did not make a carburetor during 1957 production or prior which would bolt to the standard 300C dual quad intake manifold. Manifold #1828027 may have been designed to accept then available Holley four barrels similar to those used by Ford.  There had to be engineering drawings at a minimum at the time of the technical report to support assignment of the part number. The manifold was apparently never "released" from engineering for production due to the 6/6/57 AMA ban on corporate racing participation.

John Wiman, Kiekhaefer's Auto Project Engineer, has the answer for us.  He states that one of Chrysler's Vice Presidents of Engineering would put anything into print that Kiekhaefer requested.  This carburetion option gave Carl flexibility for a 1957 NASCAR campaign. There is photographic and oral evidence regarding the Road America competition models that Carl experimented with Holleys for the 300C. As far as we know, only Carter carburetors actually came with or were factory available for the Chrysler 300C.

Every 300 ever produced used Carter carburetors. The history of the company follows traditional patterns; inception based on the ambition of one man, ultimate success, and ultimate downfall due to industry changes, government interference, and environmental regulation. 

William Carter was born in 1884 in Union City, Tennessee. As was common with most industrial pioneers  of the time, Carter had only five years of formal education. At 17 years of age, he demonstrated a flair for mechanics and opened a bicycle repair shop. In 1902, Carter  moved to St. Louis, which was the largest city within a reasonable distance of his birthplace. Carter naturally became intrigued by automobiles, and he quickly found that the carburetor was a particular source of problems for early motorists and auto companies. This prompted him to tinker with methods of improving fuel delivery, beginning with wooden models that then became cores for sand molds and an eventual cast-brass carburetor. Quickly, Carter carburetors were acknowledged for their superior accuracy in processing and metering fuel. 

In 1909, with the financial backing of a friend, the Carter Carburetor Company was born. In 1922, American Car and Foundry Company expanded into the automotive field by acquiring Carter Carburetor.  (ACF Industries traces its history to 1873.)  A great milestone was reached in 1952, when the first American-built four-barrel carburetor was produced by Carter and used by Buick on its straight-8 engine.

It was common then, as today, that many  military vehicles were modified versions of civilian products. Being designed for severe duty in the battlefield, along with the ability to perform in situations that most civilians would never experience, tended to improve the product for the consumer. It was commonplace to have modifications made for military service trickle down into the production piece and result in a better final design. This was the case with Carter because they were called upon to militarize a series of small one-barrel carburetors for use on the Willys-Jeep inline four-cylinder engine. The main considerations were waterproofing the carburetor for deep-fording vehicles and designing it to perform at extreme angles. The Carter Y-S carburetor, model 637S, then became very popular as a retrofit to other vehicles that were used off-road due to its simplistic two-bolt attachment and engineering attributes. 

Carter continued on through the 1970's as America's preeminent carburetor manufacturer. The WCFB gave way to the AFB and AFB competition series, then the AVS (Air Valve Secondaries) and finally the Thermoquad plastic bodied carburetor. 

American Car and Foundry owned the Carter property from 1956 to 1985, then deeded it to the Land Reutilization Authority of the City of St Louis. The facility was permanently closed by AFC in 1984; carburetors had largely been doomed to extinction and were no longer profitable. Edelbrock continues to produce a pretty good replica of the AFB to this day for die hard racers and restorers. The removal of PCBs found in transformers and other items located on the property led to an endless EPA battle, resulting in 20 years of legal mumbo jumbo. EPA cleanup orders and lawsuits against the many owners of the property supposedly culminated  September 29, 2005.