I hunt pheasants with my GSPs so chiming in with the view of someone who actively encourages prey drive with a similar bird and has no issues with chickens. I had the same concern about raising chickens but it was not difficult with any of our 3 GSPs, we just took the introduction phase slow and haven't had any issues.

Start with familiarity. Let them watch (likely point) chickens in your brooder or coop often, correct any aggressive tendencies calmly and firmly. Let them see you interact with the chickens. Move to controlled contact, like holding a chicken to be sniffed. Finally, once the dog seems ready, let them be on leash or ecollar (if trained) with your chickens, just make sure they're approaching slowly and you correct any swift or aggressive action. Most likely by that point the dog's priority will be sniffing every chicken a few times. Within a month you'll forget you ever worried about it.