If there is a cradle involved, your troubles are over. Hoist the boat and cradle onto a car hauler and strap'er down. Even if there is no cradle, you can build one with stout lumber to get the job done. Be sure to cross-brace like crazy. The real question is "How far?" 5 or 10 miles on good roads is about all I'd do if you used lumber. Now, if you plan on storing at home, or trailering, you might as well buy a trailer off Craigslist and modify it.
At any a rate, I found this link on Google. Might be a good read for you.