I have an '05 F150 4x4 with the 30 gallon gas tank. The tank takes up nearly all of the space between the driveshaft and the frame on the left side of the truck. Has anyone put duals on a truck like this? If so, how?

 

Welcome to the site.

Where the pipe joins on the passenger side, cut that out and run the two pipes on the passenger side, and as you get closer to the rear axle, start makeing one of the pipes go back towards the drivers side.

It is pretty easy, and a good exhaust shop shouldn't have any trouble.