On a 99 dodge ram sport 5.9L is the fuel line the 3/8 silver metal line that runs down the drivers side frame?

 

You posted in the wrong section. Moving for you.

 

Most likely....the fuel line is 3/8" and it connects to the fuel rail on the driver's side. it then changes to a flexible type hose and runs back along the trans and the driver's side frame rail where it connects to another metal line leading back to the fuel pump.