I’ve had several .308 ARs in the past, built and bought. Everything from 10” to 20”. Was a huge fan.
I think if I were going to do that again, I’d just buy a POF and skip the tinkering and parts compatibility gambling game. The POF have excellent quality, awesome reliability, no gas/tuning issues, and they’re pretty much AR15 weigh class while still slinging a .308 bullet.
IMO, the introduction of the 6.5G and 6.5CM really diminished the use case for 308 ARs. There’s little reason nowadays not to select a 6.5G AR15 for a DMR/scout rifle or precision SBR over a .308 (of similar length) and there’s little reason not to select a 6.5CM for an actual precision rifle. So the .308 is kind of limited to this heavy-hitting turn-cover-into-concealment intermediate hunting range choice... not that there’s anything wrong with that. But the moment agility matters and/or shooting over ~500 yards the .308 is simply outclassed by lighter handling and/or lighter recoiling weapons.
TBH, I ended up getting a Tavor7 some time ago and subsequently ditched all of my .308 ARs ... it was just no contest. You can find them frequently <$1800 new and they’re no shit as short as my 10.3” AR15. Cool guns, reliable, super easy to handle and carry and just pounds shit like a hammer. Excellent urban type gun or field hunting gun.