Driver's side front. The 3.9L is a version of the 318 c.i with two cylinders chopped off. In 2005, the engine choices were 3.7L or 4.7L. Chrysler's numbering system is 1, 3, 5, front to rear on the driver's side, and 2, 4, 6, front to rear on the passenger side.
Most likely the spark plug socket you need is 5/8". Older engines used 13/16" spark plugs.
For others researching this topic, this article may be of help:
https://www.2carpros.com/articles/how-to-change-spark-plugs
This video shows this job being done on a Caravan:
https://youtu.be/CE7bM8_j4Zg
Check out the diagrams (Below). Please let us know if you need anything else to get the problem fixed.
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Monday, February 3rd, 2020 AT 1:49 PM