 In this comparison, note the...  In this comparison, note the difference between small-block/429 and FE big-block distributors. The FE version on the left has three cast rings on the body's shaft, compared to two for the small-block/429-style distributor on the right. |
 Two different shaft sizes...  Two different shaft sizes were used. The smaller shaft on the left was found in 289/302s and FE big-blocks. The larger version on the right was used in 351Ws, 351Cs, and 429s. |
 From '64 1/2-'68, Mustang...  From '64 1/2-'68, Mustang distributors had a pair of shaft bushings: a long one at the top and a short one at the bottom. In 1969, the lower bushing was discontinued. |
 High-performance distributors,...  High-performance distributors, like this Boss 429 version, used dual points as opposed to the single points found in most Mustang engines. |
The '65-'67 289 Hi-Po distributors feature centrifugal advance so they don't have a vacuum diaphragm. However, nearly every other Mustang distributor used vacuum advance. Early on, single diaphragm units were used, with dual diaphragm added to most engines in '68 to assist with emissions. FE big-blocks with automatic transmissions continued to use single diaphragms through '70.
All Mustang production and service distributors have a casting number and date code, both of which help to identify the units. The casting number identifies the distributor right down to its specific application. For example, casting number C5GF-12127-A (the 12127 is cast into all distributor bodies, while the C5GF and A are stamped) indicates a unit that was originally used for a '65 Mustang with the 289 four-barrel engine and four-speed manual transmission.
To identify the application for model year, car line, engine, carburetion, transmission, and even emissions equipment in some cases, there were hundreds of different casting numbers for Mustang distributors. To decode them, use a cumbersome Ford Master Parts Catalog for your Mustang's year, or simplify matters by ordering a copy of the High Performance Ford Engine Parts Interchange from Cartech or one of the Ford Parts Identifier manuals from Warner-Roberts Products. Those books include identification numbers for many Ford parts.
The three or four-digit date code stamped below the casting number identifies when the distributor was produced. For '641/2-'67 FoMoCo distributors, the first number is the year (5 equals 1965, and so on), the second digit is a letter for the month (A for January, B for February, and so on, with the exclusion of I), and the third digit is a letter for the week of the month (A is the first week, B for the second, and so on). The later Autolite and Motorcraft distributors follow the same pattern for the first two digits, but the last digit or digits indicates the day of the month. For example, an Autolite distributor with date code 8M11 was produced on December 11, 1968.
Unless you're preparing a vintage Mustang for concours competition, the date code and even the casting number is not that important. However, if you want a vintage appearance and the correct access hole for your factory wire or PerTronix harness, this guide will help you find the right distributor.