i do quite a few stem swaps.
(which means taking the steering stem from one lower triple tree and installing into a lower triple tree from another model)
this allows us to put modern brakes,suspension,and wheels on older bikes.
i mainly do this for kawasaki kz 1000's.the process is the same for any model mostly.

if the stem is welded in i have to first remove the weld that keeps the stem and tree together.
you can grind them out.
but,
i have a lathe >;).
so i machine the weld out .