Alex,
These are phosphor-bronze liners, are are best suited for engine with positive oil lubrication to the top end. I think they will be prone to seizure in your application. I have seen folk sprinting DT machines with bronze vailve guides, but they have the advantage of being able to directly apply a few drops of oil to the exposed valve stem periodically. I think you will be better off with the original cast iron, which is more tolerant to erratic or nil lubrication. I do not know of any cast iron valve guide liners. I have heard that the Norton Commando valve guide has the right outer diameter, but as it lacks a flange a snap ring groove needs to be added. Also I belive these are used with a Triumph and/or BSA valve which has a smaller stem diameter. But one can ream the guide out to a larger size to suit, of course.
-Doug