Will a 2000 Chrysler Concorde 3.2L alternator fit 300m?

No, a 2000 Chrysler Concorde 3.2L alternator will likely not fit a 300M. While both are Chrysler vehicles and use similar engines, there are subtle differences in mounting points and possibly even the electrical connections between the two models that could prevent a direct swap. You'd need to verify part numbers for compatibility or risk it not working or causing damage. Always check with a parts store using your vehicle's VIN to ensure you get the correct alternator for your 300M.