Look I may know a thing or two about building one of these from scratch. I didn't even use plans. If you have the talent or Iron will required to undertake this task them you have already made that decision. Yes find out the legalities before starting it may give you a few large flaming hoops to jump through. If then it seams that you can't get away with it build a kit.
OH buy the way you really start with this.....
check out my gallery for inspiration,
Patrick