All of the OE Holley four-barrels used on factory Mopars were of the 4160 variety, using vacuum secondaries and a fuel balance tube that ran between the bowls on the driver side, with evenly sized barrel openings when viewed from the bottom. The easiest way to differentiate them from other Detroit versions is again the throttle-stud mounting bracket. The fuel line inlet is at a downward angle on the driver side as well. Other than that, they're similar to most others of that time.
In 1969 Chrysler selected Holley for the new triple two-barrel layout, commonly called the Six Pack after Dodge's slogan. These used the throttle-stud bracket specific to Chrysler on the primary (or center) carb; the secondaries have no metering blocks and large vacuum spring housings and all use a fuel line inlet located at a 45-degree downward angle on the passenger side.
Some Final NotesThis article is a basic introduction. There are several sources for additional information, primarily books published by Galen Govier's GTS company. These books come in a variety of pocket-size formats and are an invaluable source for those seeking date-code information and parts for specific model years. For servicing, performance, and emissions purposes, virtually every application used a different part number, creating literally dozens of numbers, despite simple physical interchangeability between models.
Parts for most Holley carburetors are still available, though some Carter models may be difficult to find small parts for. Don't overspend on models with heavy modifications for competition, which may require serious rebuilding. The Carter units are now being manufactured as a subsidiary of the Edelbrock performance line.
Carburetors were one of the most delicate and fragile parts on any car and subject to the corrosive effects of fuel. Any used carb should be rebuilt and checked thoroughly for leaks and damage before being put into service. Spilled gasoline on hot intake manifolds is a recipe for certain disaster.