By "load boards" do you mean Uship? There are precious few expedite loads that ever end up on publicly accessible load boards. Visit a truck stop and see how many flatbed expediters you find (there won't be many). Call expedite carriers and find out what they say about flatbed for expedite (it won't be encouraging if you're set on a flatbed truck).
A 24 foot box truck with a sleeper is all that and a bag o' chip in the expediting business. Even better if you have a co-driver to keep it moving while you're sleeping.