Hello
I use KTM690 ENDURO R 2012 front fork on my XTR. It has 250mm travel but would like 300mm what I got on my KTM690 EnduroR 2011 before I sold it. About the brakes do you really need two discs or is it just that to see original?
It,s gonna be a fail compared to XTR travel 225mm if you use KTM 990 fork or you change the springs to stiffer ones. Did you got the clamps as well with the KTM forks? Dont,t know about your stem but just sold my original front fork from my XTR to one guy who got a XT660X. It seems that it,s bolt on to the clamps so in your case if you want to do same conversion that I did it should not be to much job!
http://www.xt660.com/showthread.php?t=20031&page=2