I guess you could cut off the stock fender there at the rear of the fender kind of flush (radius cut) with the front of the new cowl. Then fill the gap with some new sheetmetal and weld it to the inside of fender to close up that hole. Cut a few louvres in it. You could hide all kinds of stuff behind there. Ignition Coil, computer, windshield washer jug etc. I like your cycle fender idea too. A 300 cu in FoMoCo straight 6 with side draft carbs would be bitchin too. Neat project!