New high-pressure fuel hose is installed before the tank goes in. We stress high-pressure hose for its fuel resistance to today's harsh fuel additives. It's the same size as low-pressure hose, but much stronger. Call it life insurance for old Fords. Most big-block Ford applications have a 31/48-inch fuel line. Small-blocks have a 51/416-inch line, though we recommend a 31/48-inch line for high-horsepower small-blocks as well.