I work for a large defense contractor and my company does pretty much exclusively phone interviews, boy it suuuuuuucks. I tend to pace around the house quite a bit, so I make sure the family knows. Make sure my wife takes my toddler out to play or something so I can have my quiet pacing place, haha. The interviews are usually quite technical for my field, so I can't use any replacement words really. If you block like I do, it never hurts to ask for a quick second to regain your breathing and your composure. Remember, they honestly don't care if you stutter, as long as you know what you're talking about, prepare beforehand, be respectful, etc. Especially if they are asking you if you're interested. My company has offered to do a Skype interview so I could write my responses down as well. See if that is an option.