The first thing is that the two front wheels need to be casters.So you would need a second bake to cut up. You would need to take the tubes that the bike forks go through off of both bikes and build a new front end. Then you need a steering setup. The steering would have to work both wheels, of course, but it couldnt turn like a regular bike but more like a car. Look into how riding lawn mowers steering works. i dont know exactly what you are going for but it sounds like more work than its worth. I would say if your going to go through all of this work then try for a recumbant style bike, i dont see turning a regular bike with two front wheels being easy or pleasant.