I installed one of these kits. It uses a reduction gear box and works well. It uses the 76mm clutch so swapping engines is a snap. Since it is braced by the rear axel and seat down tube it would be a candidate for mounting this kit in frame. That would require a longer rear axel, but most good hardware stores can supply this.
Try this link for directions:http://motorbikeworks.com/directions...tion%20pdf.pdf