I strongly recomend that you take a couple of chain rollers, inner and outer as they gave us and other XT600 riders trouble on the road.
If your rear suspension is fresh and the pre-load set correctly for your load you may not need them, but they are small parts to carry and prevent the drive chain cutting through the frame. It's also worth visually checking them every time you lube the chain, very easy once you have spotted them for the first time (one above the top run of the chain, the other below the bottom run)
I would also take a set of front and back brake pads and possibly a front sprocket (you may well be able to find a rear sprocket and chain locally, the front is more unusual. Also, as it has roughly 1/3rd the number of teath as the back it probobally wears three times as fast, some people recommend changing it before the rear and chain, to extend the chains life, though I have never bothered.
Oh, and a couple of the tab washers that retain the nut that holds the front sprocket on, ans possibly a spare nut too, as I am told that they have been known to come off & disappear