The magnaflow catback is one of the best tones on an F150:
http://motorhaven.autoanything.com/exhausts-mufflers/60A1835A0A0A1906108.aspx?kc=MOTORH
the Bassani Aft cat is also a killer one as mentioned earlier:
http://motorhaven.autoanything.com/exhausts-mufflers/61A2685A0A0.aspx?kc=MOTORH
We'll also help you with a deal at MotorHaven, feel free to ring us up and John or Charles will be happy to serve any FTE member