Griff has a great point as well. You can't go overkill on the drawbar and ball either. Southern States sells heavy duty draw bars that are solid steel as well has 25,000 lb rated balls.
Also check here
http://www.etrailerpart.com/hitchballs.htm
as well as the links on my past threads.

I even went so far as to have one of these custom made for my application:
http://www.trailerguardian.com/

Sorry , i have to disagree with sydwayz on towing with the navigator. Have a 2000 expedition and put the heaviest hitch I could find , tows great. I have a 29 with twins and dual axel trailer. Factory tires sucked , a bit of sway due to the soft sidewalls. Get some good truck tires and you'll be ok. As far as power at the ramp , low 4 has more than enough power to pull that little scarab up the steepest of ramps even if you have the 4.7 , the 5.4 is better. Have used my buds 05 navigator on occasion and workd just as good as my setup. Good luck!