I've considered doing this forever. Sketched it up a few times, drew it out on the garage floor. One day...
In my part of Ohio you can get away with anything, but apparently there is an issue with using ATV parts in the front end. Unfortnately that was part of my plan! If I just fly under the radar it's easy, and if I want to get all fancy (apply for a VIN, etc) I'll have to prove I bought everything, show lights and safety equipment, and hope I get the right inspector!!! So under the radar (still legal, but will still have to explain it if I get pulled over) it is.
One thing I will do to keep the VIN in a reasonable spot is to reuse the headtube as the steering column, right behind a steering wheel. Handy, and funny.