I am gaining some experience working with fuel & brake hardlines, so can offer a bit of advice.
The copper-nickel alloy lines available through many parts stores are highly recommended. Porsche and Mercedes have been using this material for brake lines for at least 20 years.
A lot more expensive than the steel lines, but easier to work with & assemble and most importantly they are corrosion proof.
For fuel hardlines I use the brand "Cunifer". They are the same copper-nickel alloy but available in the larger Metric sizes and suitable for the long lines that run under the floor of the 924 and 928 and 944, etc.
Though this might help.
Len