I would think, by now, all of the allocations have been spoken for or used by dealers to order trucks they plan to use as lawn art to sell normal F150's. Finding an unspoken for allocation that can still be built the way you want it may be like finding the needle the the proverbial haystack.
Definitely the case with the dealer who normally hooks me up. All of their allocations are already used for the year (they only had 25 allocations though). They're still taking deposits in case people back out but he told me people are basically getting in line for MY2018. I'm probably waiting till 2018 to order anyways but I may have to throw down a deposit now or I may be too late.