This is Bernard's thread if you've not found it already:
http://xt660.com/showthread.php?t=14756
I'm currently trying to decide which way to go with converting mine. The bolt-on solution is all very nice, as long as you have about �2500 sitting around - bearing in mind even if you buy the kit you'll still need to find a front wheel and disc from somewhere. If you're in a hurry (lets say, hypothetically, you've already sent your entry in for the Heroes-Legend
), then I agree the kit would make some sense.
More tempting for me is to go to OTR for the yokes, and put the rest of the front end together out of 2nd hand KTM parts. Ok you're then going to have to have the forks resprung and revalved, but it's still basically a bolt-on job with no machine-shop requirements. And I'd guess it would come out about half the cost of the full OTR kit.
I have (and/or have access to) the expertise and machinery to do something a bit more clever, either making KTM (or KLR, as Bernard did) yokes fit with a custom stem, or even making a set of yokes. But I'm not sure I could make it pay off cheaper than the 'middle' solution above, and it would certainly take longer.