I also used Fuel Injection rated rubber fuel lines. It seems that any parts store is best served to only offer fuel injection rated fuel lines, in case someone not knowing there is a difference in non-fuel injection vs fuel injection ratings sells the wrong, weaker fuel line when the higher pressure designed fuel line was needed. I don't think I could get non-fuel injection rated fuel line from out local AutoZone. I know when I purchased some fuel line from them the other year, so I could replace the fuel lines at the fuel tank, fuel pump, and fuel filter, the line I got said it was fuel injection (high pressure) rated - fine with me.
Anyway, despite what caused you to want to replace the fuel lines, I am glad you are doing it. I have only seen a few cases where the rubber lines at the fuel pump, or the fuel tank, caused a problem on vintage First Generation Mustangs or Shelbys. But, I can't say the same for the rubber fuel line at the fuel filters that screw into the carburetor. Those are under pressure, albeit only 5-7 PSI or so. But it is enough to weaken those rubber hoses at the carburetor sooner than the other locations rubber fuel lines are used. I repaired more than a few underhood fires caused by those fuel lines at the filter beginning to leak liquid gasoline near the distributor that is located at the front of the engine. Pooffff... The lucky folks it happens to have good insurance and the car is totaled. The less lucky are either un(der)insured, or the insurance company pays to get the problem fixed. Although I would always get the car back into good operating condition using new parts, I would often have an adjuster who wanted me to installed used replacement parts, and just wrap or tape up damaged electrical wires. I never succumbed to the almost veiled threats of no future work if I did not comply. I did the job correctly. But, I am sure others were not as enthusiastic about wanting to do that kind of job properly.
Okay, that dead horse is well beaten. So I will now step back, at least a little. I see Cleveland Crush mention the rubber fuel lines ought to be replaced every 10 years. I do not disagree, but for the carburetor fuel filter's rubber fuel line I would say replace it annually, whenever a tuneup is performed. In a similar arena, I know I really ought to change the hydraulic rubber hoses for our braking systems on all our cars. In our vintage Mustangs and Shelby they are, to my knowledge, all original. They look pretty good for being 50+ years old, with very minor checking. And I usually subscribe to the "Don't fix what ain't broken," line of thinking. But, this impending Car Season is anticipated to be quiet as I did a lot of work on those cars last year. And I am looking at things to do this season. I have already replaced the fuel lines on the 73 vert, and ought to replace them on the other two vintage ponies. And all three should have new brake hydraulic lines installed, along with a flushing and use of new DOT 3 disc brake fluid. That would be a somewhat costly set of maintenance operations, but money (and time) well spent. I am so glad this thread came up, as it had helped me zero in on what I ought to be doing this Car Season! Woo Hoo, I have renewed purpose in life!
An aside, for anyone who has not replaced fuel lines at the fuel tank or fuel pump, I have a YouTube video showing how I do it. I know it sounds like it ought to be a no brainer procedure, But, I promise you there is more to it than just, "All you have to do is." Neglect looking at the YouTube video at your own peril if you have done that kind of work before. It is easy enough, but you really need to know what you are getting into to prevent some serious problems along the way:
https://www.youtube.com/watch?v=lkKVcliOd2w
