i am almost exactly the same size as you are - same height and within 2lbs. and to tell you the truth it depends on the ski. i rode a 178 invader a 176 pipe cleaner and that was perfect for me. those sound like the kind of skis you would be looking at- i mean very generally. but there is some range too. because i also rode and elizabeth last year (172) and i ride a ARG on powder days (185)
im basically repeating whats said above, but anything between 173-178 you wont go wrong with. just dont go shorter than 172 or longer than 180 and shell be right!