I'm going to be making a bunch of upgrades on my fuel system and I'm wondering if I need to replace the fuel lines due to the ethanol in gasoline these days. I'm currently running aluminum lines for the feed and return lines. Would I be better off with mild steel, stainless steel, or PTFE lined hose?

I've been told that all you need to worry about is no mechanical fuel pump because of the diaphram. I am hoping if I m incorrect, someone will jump in.

You're fine on the metal lines & modern neoprene parts (hoses/carb parts etc), the composition of them has been changed so that applicable parts manufactured for decades now are way more resistant to (E10) ethanol than the old stuff so you're good there

Buy fuel injection hose with the proper FI clamps. It is designed for ethanol. Regular stuff rots from the inside.