Speedflow fittings/fuel tank

If I am using 3/8" fuel line what size push-on Speedflow fittings do I use? They go from "-4" to "-20".

Has anyone modified the standard LJ tank to accomodate dual pickups at the bottom rear? I'm doing this with two 3/8" pickups to a Y- piece and into a Holley red (then a surge tank, but that's another story).

Thanks.

3/8" is -6AN

Thanks dude.