I thought all speedos spun the same way. For instance, Dime City sells a bunch of speedos but there is no reference to the way they spin. In other words, there's no left hand and right hand version for each model.
Per the Honda parts fiche, the same speedo was used on '77 and '78 K and F bikes. The best I can tell, the bikes with wire wheels had the speedo drive on the right and those with the Comstars and a single disc had it on the left.