1971 duster brake lines?

Stainless is a turd to get sealed because it is so hard of material
You are 100% correct on that, but I still always buy stainless because of the corrosion resistance and because it just looks good basically forever. I have had issues many a time with tightening stainless brake lines, you sometimes have to really get them tight to get them to seal, but as of yet I have not damaged a stainless brake line tightening it down, although I am sure that eventually my luck will run out.