For the most part, those decoders are based on the research of Galen Govier. He has published this research in his white books, also known as pocket books. They are good resources and available on his website fairly cheap if you're interested in obtaining a copy for yourself. He has being doing this for a long time, and occasionally updates the books with new info. It possible that the online places copied both the outdated & the updated info. A lot of those online decoders copy from each other and don't really do any research of their own. If they do any research on their own, that research is prone to be be incomplete or questionable.

The biggest problem with almost any decoder is that they try to simplify the codes over a period of years and models, but in reality, the meaning/availability of the codes can change between years/models, and different models often use different parts for the same code. This is especialy true of grouped items like option packages.

For example,...

A Challenger trunk light won't be the same as a Roadrunner trunk light, even though they may both use the same trunk light code.

The 71 Challenger M42 molding is a different part from the 72 Challenger M42 molding.

M88 tail panel molding is 4 piece stainless on a 70 'Cuda, but the same code in the same year on a Gran Coupe Barracuda is a 3 piece aluminum molding.

Sometimes a code will not be used for a year, and then come back meaning something entirely different. You'll see that in the decoders when they try to add info from the late 70's or the 80's on top of the musclecar era stuff.


Even though M42 doesn't appear to have been used on 70 Challengers, it may have still been used on other mopars in 1970 and even in 1969, so the decoders would list it as M42 1969-1972. (this is just an example, M42 doesn't appear to have been used on anything in 1969)

For a decoder to really be reliable, it needs to be make and model specific.

Tav