Look into a Honda Baja kit. Find out what is all in there and then buy the yammy parts seperatly...or maybe yammy makes a kit like the Honda Baja kit. I would assume all you would need is headlight w/ brights, tail light w/ brake light, turn signals (maybe), mirror(s) and a horn that is audible from like 100yds. I'm sure if you check with the IN DOT they can tell you for sure. I know that in NE if you are in a rural area, you just tell them its street legal they'll believe you and give you a plate.
D