I think the biggest problem is that the OP was likely borderline to get invites at most programs already--the match rate for someone with his step 1 score was already only ~60%, and this failure will hurt.
THAT SAID: I'm a strong believer that if you have your heart set on a specialty that you shouldn't do a backup specialty and you should go all-in at least once. The reason is that if you hedge your bets, you're going to lower your already tenuous chances for the specialty you really want even further by spending time getting a second application ready. While going through the SOAP or taking a gap year sucks it's not the end of the world, and at least you can say you gave it your best shot. FM/PM&R/whatever his second choice specialty would be will still be attainable for an allopathic applicant who delayed graduation by a year. It also opens up the possibility of doing a surgical prelim year, as someone else said.
Plus, it's pretty late in the day to call an audible into another specialty or try to throw together a backup application. You're not in a great spot, and honestly you may at best be a coinflip to match, but if your connections and research is as good as it sounds I don't think your app is DOA.