The lines are metal and rubber
Myself i would drop the tank,either clean or replace and pressure test the fuel system,fix any leaks,then run it.
If the old lines don't leak i wouldn't change them,replacement rubber lines may be made of inferior rubber and only last a few years.
I see that a lot new trailers with rotten valve stems made in China,yet old tires from the 80's the stems are still good.
90 Chev 3500 c/c 4x4,6.2na,400 auto,4:10 gears.DSG Timing gears,main girdle, isspro tach, pyro,boost,oil and trany temp.Dual Tstats, High volume peninsular pump,on shelf, Custom turbo and intercooler 85%complete. Change of plans for the dually, it's going to get a Cummins. Both trucks are Blue 90 4x4 crews