I was just at the Portland, OR auto show and Ford had a sticker on all of their vehicles saying if you did a test drive that day you'd get a $1500 voucher and you could add that to the current $1000 rebate for a custom order. It didn't seem like there were many restrictions other than models like the F150 Lightning, Shelby GT500, etc.
Not sure if Ford's production part situation is better than GM's? Either way, Ford seems to be getting aggressive with pushing the custom build process. From what I've gathered lurking on the Expedition forum, Ford has a much better portal for you to check on the status of your build.