I looked into this last time we talked about it thinking along the lines of commercial or special purpose vehicle, but I think I just had an idea and found something to back it up. I think with these Dodges, and maybe some other vehicles, it simply comes down to the build date of the specific vehicle.
Here's what I found;
"Side Marker Lights
Effective January 1, 1968, all passenger cars built for sale in the United States were required to display amber lights or reflectors on the sides of front fenders, and red lights or reflectors on the sides of rear quarter panels.
Standard No. 108 - Lamps, Reflective Devices, and Associated Equipment - Passenger Cars, Multipurpose Passenger Vehicles, Trucks, Buses, Trailers, (except pole trailers and trailer converter dollies), and Motorcycles (Effective 1-1-68 for vehicles 2,032 mrn (80 or more inches) in width and effective 1-1-69 for all other vehicles). This standard specifies requirements for original and replacement lamps, reflective devices, and associated equipment. Its purpose is to reduce traffic crashes and deaths and injuries resulting from traffic crashes, by providing adequate illumination of the roadway, and by enhancing the conspicuity of motor vehicles on the public roads so that their presence is perceived and their signals understood, both in daylight and in darkness, or other conditions of reduced visibility.
Confused yet? Basically, what this says regarding side marker lights is that effective on all vehicles made on January 1, 1968 or later, amber side marker lamps or reflectors that can be seen in profile are required to be included near the front of the vehicle, and red side marker lamps or reflectors that can be seen in profile are required to be included near the rear of the vehicle.
Initially, the regulation for 1968-1969 required lights or reflectors, which is why some cars in 1968 had amber lights in front and red reflectors in the rear (1968 Ford Motor Company cars, for example). Chrysler vehicles used lights in 1968 and reflectors (on most models) for 1969. This regulation was later amended to require lights and reflectors on all vehicles made on January 1, 1970 or later, which is why most lines had changes to their side marker lights for the 1970 model year.
The regulation required that the side-facing lights and/or reflectors make the vehicle's presence, position, and direction of travel clearly visible to other drivers approaching the vehicle from the side, or at any angle where the headlamps or tail lamps of the vehicle being overtaken cannot be viewed. In other words, other drivers should be able to see your car in darkness regardless of the direction from which they are approaching, and from the color of the light or reflector, be able to tell at a glance which direction your vehicle is facing or moving.
The amended regulation for January 1, 1970 also included the requirement that the parking lamps remain lit during headlamp operation, and that side marker lamps be illuminated whenever the vehicle's parking and tail lamps are on. The parking light revision to the regulation was to make vehicles with a non-functioning headlamp more noticeable to other drivers, and lessened the chance that it might be mistaken for a motorcycle by oncoming traffic.
In 1970-1971, most Ford Motor Company vehicles were equipped with flashing side marker lights that corresponded with the turn signals flashing in the direction of a turn. This was eliminated for the most part for 1972, although many General Motors cars utilize a flashing front (amber) marker light to correspond with turn signals to this day."
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