The baseband is NA2 and the build number is NA6 they're one and the same afaik.
As for installing a custom ROM well you can install NA6 based ROMs only like flexkat, sweetrom kingdroid and crashrom. But not CM or older builds of said ROMs.
Sent from my SM-N9005 using XDA Premium 4 mobile app
// Nexus 5 (D821) // Liquid // UBER //
Note 3 (SM-N9005) // AOSP ROM of variety // Lean or temasek's Kernel // - Dumped. No more Samsung