fitting internal passages restrict fuel flow rates

[Grumpy]

-6AN fittings and dimensions

I just noticed all the -6AN fittings I have, have a 5/16 or smaller id hole! The -8AN fittings have a hole big enough to completely insert a 3/8 copper line into.

Can I assume that -6an is sufficient to plumb the fuel pump ports to the filter reg ports? And then -8AN from the filter output to the 3/8 fuel line and up to the fuel rail in front?
-8an would be pretty large to run between the pump and filter.
I really doubt the smaller lines would matter on a stock motor.
May still use factory vinyl...

https://www.anplumbing.com/

thats a good point that almost everyone ignores, people just assume that a 3/8" oe AN#6 fuel line can supply the engines needs, few realize that the internal fitting passages vary a great deal between manufacturers and that AN#8 or 1/2" line is a much better choice if you intend to have the fuel system deliver fuel and produce over 500 hp, I see so many guys that throw on bigger heads and a longer duration cam, and few think about the fuel line size, the fuel pump and fuel injector size let alone the fuel pressure regulator or fuel pump and filter inlet port size or fuel line sizes of fuel pressure regulator or fuel filter flow rates required.

http://garage.grumpysperformance.com/index.php?threads/setting-up-your-fuel-system.211/

http://garage.grumpysperformance.com/index.php?threads/how-big-a-fuel-pump-do-you-need.1939/

http://garage.grumpysperformance.com/index.php?threads/calculate-fuel-injector-size.1200/

http://garage.grumpysperformance.com/index.php?threads/input-on-electric-fuel-pump-selection.10664/

http://garage.grumpysperformance.com/index.php?threads/fuel-line-sizing-return-vs-feed.3067/