what dirt bike triple tree will fit the 929

 

One that has 50mm holes spaced out the same width as the 929 triple

 

Headset stem has to be same length, but berring size is going to be a huge issue....also the 929 has a larger bottom berring than the top.
I just tried to put 07 gsxr 600 triple/front end on my 929 and its way easier to just use 929 triple with any 50mil fork.