After market triggers are absolutely forbidden.  A Krag must be as issued.  This also includes bedding the barrel and action.  The lone exception is you can modify the peep sight by enlarging to no more than 0.1 (the Sgt Peep on the 1902 rear sight is hopelessly small at 0.04 dia.).  I enlarged mine to 0.07, which is about as large as you can go without ripping open the peep, rendering it useless.