Looking good. I'm no help for the return line. Good idea on leaf spring bushings at this time while they are easy to access. I actually flushed the inside of my frame with lots of water at this point, before placing the cab and bed back on. Then poured some oil down inside the frame rails, lifted the frame from one end, then the other so oil would coat the bottom surface. Oil dripped from the frame holes for maybe 2 weeks then stopped.