Wow, I'm shorter than 5'7'' and my 565 (same geo as a 585) in 51cm is running a 110mm stem and has a reach several centimetres longer than that set up!
It's still actually shorter and higher than I used to run my Giant TCRs, and I had a 49cm Look as well in the same geo but it was definitely too small.
Based on those reach figures you're going to struggle to get the 381 to fit properly. The shorter seat and head tube is going to make the saddle to bar drop pretty big and you'll need a tiny stem.
Incidentally I think the 381 in 52 above would fit me well - slightly too long but I've got short legs for my height so the seat/bar drop wouldn't be an issue. That gives you an idea of how different our respective set ups are even though you're taller and are after the same size bike as I ride.
Wow, I'm shorter than 5'7'' and my 565 (same geo as a 585) in 51cm is running a 110mm stem and has a reach several centimetres longer than that set up!
It's still actually shorter and higher than I used to run my Giant TCRs, and I had a 49cm Look as well in the same geo but it was definitely too small.
Based on those reach figures you're going to struggle to get the 381 to fit properly. The shorter seat and head tube is going to make the saddle to bar drop pretty big and you'll need a tiny stem.
Incidentally I think the 381 in 52 above would fit me well - slightly too long but I've got short legs for my height so the seat/bar drop wouldn't be an issue. That gives you an idea of how different our respective set ups are even though you're taller and are after the same size bike as I ride.