https://www.ebay.com/itm/1985-Yamaha-RZ350/233959580077?hash=item367913e1ad%3Ag%3AkJAAAOSwKF9gbkgo&LH_ItemCondition=3000
That bike has been for sale for a long time now.
Why he would go to the expense to build a 421 motor and then put on a single carb kinda boggles my mind.