You can do a crank mod on the XT M771 model,it has a longer spindle so the only thing to do from 68/73mm to 83mm is to get the spacer out and grind down the granny tabs.You also don't need to use the BB spacers.
The XT crank arm on the non drive side doesn't fall off since the spindle is now long enougth for 83mm BB.
The XT crank arm on the non drive side doesn't fall off since the spindle is now long enougth for 83mm BB.