To do this you must have a Headless Horseman Mount.
Otherwise, this one pretty much speaks for itself
1. Join the party of you're friend who owns a mechano-hog
2. Mount up on you're headless horseman mount
3. Jump into you're friends mechano-hog
4. ???
5. Profit
http://i99.photobucket.com/albums/l309/bluejoelol/1.jpg
Ride around... In style.