just finished running all new brake lines now its time for new fuel lines. i already got a brand new intank fuel assemblty but did not mark which line went to which part of the motor. Im guessing the thinner of the two lines is the return and the thicker is to the motor. Am i correct?

 

Look in Infidels gallery, he has a side view of a 12V showing where the lines are, but you are essentially correct, the 3/8" line is delivery and the 5/16" is return. Return is behind the fuel filter, kinda a bugger to get to.