My company has decided to replace my hot shot rig. I am woundering wich would be the best choice 350,450,550? I currently have a 350 7.2/6speed manual and pull a 30 ft gooseneck from coast to coast. I am woundering about the 4.30 & 4.88 gears, what kind of fuel milage i would get at 70mph.

 

You need to check out the forums that handle those rigs since this one is used for introductions. The Superduty or the Towing forum would be a great place to check in and ask your tech question there. The Forum tab at the upper left will open the list of Forums up for ya.