Your initial issue will be those bloody filters that PDs use to decrease the # of apps they have to review. Most filters I know of (n=10) have their Step 1 set at 230. I heard a few are higher. My med school even had a honors filter that categorized you in terms of how many 3rd year honors you had...< 2 meant no interview (but that's a rarity).
With all that said your best bet is what your letters say, how you do on your away rotations, what else your app is composed of (meaning that their is always more to an app than a Step 1 score...is their something else about you that would interest them), and the calls your chair/PD make for you.
Also while this may be controversial, I would advise you do an away rotation at a place that guarantees rotators an interview. It would suck to waste 1 month at a place and not get invited back. Its definitely possible, to make it with your Step 1 score but it will be an uphill battle.
If you were planning on your Step 1 to be the only thing that carried your app then thats a problem, but if your app is well rounded and you are strong in person it should help you.