Hello, My name isXXXXX to Just Answer. I'll try and Help you out.
As the other expert was stating, the transmission is not compatible from a 05 Pacifica for your 02 300m the pacifica is equipped with a transverse transaxle which means the engine and transmission sit in the vehicle side by side, on your 02 300m you have a 42LE transmission which your engine sits in front of the transmission like a rear wheel drive vehicle. As a result the transmissions are totally different. Actually all the external accessories on the engines are totally different. It proably would not be worth your troubles to try and put this engine in your vehicle. Keep looking for an engine and transmission that comes off the same body style vehicle as yours such as an Intrepid or Concorde.
Here's some pictures of the engines in the vehicles:
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Here's the transmissions, 42le are the first 2 pics:
42le is in the 300m
41TE is in the Pacifica.
The engine on a stand for the Pacifica is a 4.0l the 4.0l is based on the 3.5l engine block...
Here's a 3.5 :
As you can see, there are several differences, that's why I say it's not worth the effort, you'll end up spending the money saved to get all the gaskets and parts needed to make it fit. Sure the base 3.5 engine is the same, Just too much stuff to switch out to make it work. Sure it can be done if you're willing to spend the money, that's why I say it's best to just get one off of the same year. makes everything easier and it's sure to fit with no problems. (just my 2 cents) Thanks.