I have done this with a Dyna. It was so much fun, I promptly bought a trailer. If I had to do again, I would find a way to level things, a loading dock or ditch, some kind of incline like a walk out basement...if I had to use a ramp again, heaven help me, it will be as wide as the tailgate. And lots of friends. I hauled once in a horse trailer using pales of hay to hold the bike. Buy a trailer. Sleep better...LOL
I know to some this is no big deal, but my bike represents an investment and cherished item. Getting my bike into the back of a truck turns my stomach.