Just purchased this kit off of ebay.
eBay Motors: 2005-2007 CHRYSLER 300/300C DIRECT iPOD INPUT +AUX CTRL (item 150215640324 end time Feb-22-08 23
40 PST)
Cost $129 bucks and well worth it. UPS dropped it off at work on my lunch break so i went out to the car and had it up and running in only 5-10 minutes. You can control it through the steering wheel and everything. CD quaily sound for hardly anything. Dealer wanted $250 for the part. $325 installed....
Glad i went this route. Seller has many of these left so happy bidding!
(P.S. Make sure you tell him i sent ya!

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