The reason why the tank in the cab makes it easier is because it frees up real estate under the truck bed, where the exhaust pipes would like to go.

The reason gas tanks are no longer in pickup cabs is the awful scenario where you roll the truck and there's up to 22 gallons of gasoline right there in the cab with you. Plus I had a tank develop a crack on a trip and it's not nice to have gas dripping onto the floor and puddling near your feet. Plus even with the windows open at speed it is still gassy enough to make you puke.

My 77ford has two tanks, one under the drivers side and one in the back. For an exhaust for its 400 I am considering coming out of the headers crossing over to the passenger side and running one 3 1/2" pipe out the back.

R.