F and K have different valve train, valves will not interchange. The 78K valves are oddballs, only year they did it. They are same size as the previous K models but they use the keepers and top retainers of the F motors. I am guessing the best way would be to get regular K valves and then get the matching K retainers, keepers and springs. I would suggest you call and talk to Kenny at Cycle xchange. One way or the other he will get you set up. I would suggest you send the head to him for the rebuild so the valve guides are replaced correctly and then the correct valve job is done after. You cant just throw new valves in and not do the valve job. More than likely the valve guides are on the loose side as well. If you dont remove them correctly you can damage the head. Why I would suggest sending the head to them so it gets done correct and with proper parts, especially with the oddball year.