I found a dealership that took my order with no $$$ down. Many have said that since it's a mustang, and will sell, they don't need to charge up front. Good thing too, since they're sticking with x-plan, and I found a similar one with the magneride for only $113 more - hell of a deal since the MR...
Before signing or giving any money? yeah, of course.
Ask for it in writing.
I made sure the two dealerships promising below xplan pricing to me got the OTD pricing in writing. If they ask for something different, I say no thanks and move on.