I drive a v6 silver mustang... but its an automatic... anyway... I was gonna suggest
www.autotrader.com ... while I was looking for stangs and there were TONS on there.. of course you will have to nogotiate a price.. most are nogotiable.. but be sure to get the VIN and check
www.carfax.com to make sure it hasnt been wrecked and such. but it will list all of the mustangs silver, V6 within the amount of distance you choose for sale by private sellers... I would reccomend it because then you wouldnt have to pay the dealer price and you would still get a great car!
I dunno though, its up to you