Doing a plumbing build and not sure what material are the fuel lines going and coming from the fuel pump made of. Are they stainless steel?

 

No, they rust so they are not SS. But then again does it realy matter what they are made of? You don't have to use the same material as the stock ones, as long as it has about the same ID.
I just bought a roll of copper fuel line, and used a simple pipe bending tool.
Easy to work with, cheap and does the job nicely.

 

Um I'm not replacing the lines I need to flare them to attach AN fittings. But in order to flare I need the right tool in case they are steel I can't get a flare tool that only does aluminum.

 

Like i said, they rust. So mild steel.

 

They are regular old, not exotic, mild steel.