Disclosing your stutter to the interviewer(s) shows emotional intelligence and incredible courage. I think they would greatly appreciate that and it’ll make you feel much more relaxed too. Apart from that, yes, preparation is key so you don’t have to think on the spot too much, which heightens anxiety and exacerbates your stutter. Do some box breathing exercises before entering the interview to activate your parasympathetic nervous system, which calms you down pretty much immediately. Most of all, be yourself. Don’t stress too much of you get blocked. Stop, breathe and start again.