a 681 you leave the way it is...too late now.
I agree with oysterer on this one.
I know, it's your gun , do with it whatever you want.
But would it have been more cost effective to buy a 686+ which comes with a 7 round cylinder and round butt, and just have the barrel cut down? And maybe have the sights changed/modified?
Again, your gun, your call. But I'd never have my 681 ND modified.
JMHO YMMV