Thanks for that. Bad enough in a pickup, but when the improperly-engineered hole gets hacked-through the passenger compartment floor, it's just criminal negligence.
My '88 K1500 has sections of plastic (Nylon?) hose in the fuel plumbing. Have every expectation they're OEM. That's how the connections to the fuel pump hanger were made.
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When I built city buses, the air brake system was a nest of Eaton "Synflex" tubing; hard yet flexible thermoplastic (Polyester? Polyamide?) with fiber reinforcement. I expect semi-trucks or anything else with air brakes is built about the same. A person could go to a semi-truck repair shop, and maybe buy their cutoff scraps and get long enough sections to fab a GMT400 fuel system. Brochure claims it's resistant to gasoline, but I've never dropped a sample into a jar filled with gas. Worst part would be coming up with the fittings to connect it to the rest of the vehicle. What we used on the buses was ordinary-looking brass compression fittings, but with metal sleeves to support the ID of the hose where the brass ferrule clamps it. MAYBE those brass compression fittings were somehow "Synflex specific", I wasn't the buyer of them, I don't know where they were sourced. Maybe get the fittings from the same truck shop you get the Synflex from.