If you find some decent lines in a junk yard, I'd advise repainting or resealing them in some way before install to ensure you don't have to do it twice. Definitely flush the line out as stated by luckyg, don't know what may be in those lines if they've been sitting empty.

Worst case scenario, make your own fuel lines. It's not much more difficult than making brake lines. IMO, the hardest part either way is just removal and installation, since you gotta wiggle it in at strange angles.