I'm currenty in the processof swapping a 01 5.3/4l60e combo into my 93z71 and have a question about the fuel lines, i know there's the supply and return up to the rails but there does the third line go that's running with the supply and return?

Any help is greatly appreciated cause I've been working on this swap off and on (money permitting since march) and am getting it pretty close to firing it up...