Legalizing my chopper-style three-wheeler?

my three-wheeler has a single person, cushioned seat with no harness, a 67cc Sachs snowmobile engine with a centrifugal clutch on it, and it has a roll cage for the engine, it has a wheelie wheel on it, it does have a differential. the front of it is like any chopper you see, 2-inch pipe connecting the front to the back. the front wheels have shocks. it uses a snowmobile throttle. it does have, or is going to have, a kill switch on the handlebars, but needs a starter rope to start. it rides about a foot off the ground. the front end does have foot pegs. the handlebars are less than 30 inches above the seat. i just want to know what i have to do to it to make it street-legal in Washington.