My metal fuel lines from stem to stern are rusted in multiple places. There are almost as many spots of fuel hose patch on the line as there are line. What is the best way to replace these?

I have talked with the dealer and the lines for my 83' 300TD are no longer available. I hesitate to use a set of used lines for fear of the same problem, that is if I could locate partable wagon. Can I use any steel metal tubing? Do auto parts stores cary a standard metal fuel line? I'm running biodiesel so copper is out.

Anyone done this or have a simple elegant cost efective solution?