Yes, you are limited with the oil clutch version. I haven't done it or know who has but it would seem you could convert back to a dry clutch version like what was used in the early 8T's.
Seems the last time I was in Versailles, MO at Zimmerman's Tractor I saw a D318 motor that was set up for a grader. I think it was a dry clutch but it was complete. As with any salvage yard it could be complete today and missing parts tomorrow. He can be a bit difficult to deal with on the phone but his number is 573-378-7210. I priced a complete air cleaner and pipe to connect it to the intake manifold for a 9UD6 over the phone and he quoted $400, but the next time I was there I made an offer for one that was less than perfect but could be straightened and he took $100 for it and the connecting pipe, saying he is a bit more reasonable in person. I suspect shipping from Missouri to Alaska would almost be cost prohibitive, but depending on what your budget might be, if you are interested the next time I'm there I will ask. Maybe some pictures? bboaz