You could lap them in to their original seats. It will work as long as the pattern is even around the seat and the valve face. One advantage is that the valve lash dimension will be little changed. The disadvantage is that it is an old method not really suited to modern engines.
Grinding or cutting the valves and seats will make both concentric again, and establish the correct seat width and placement on the valve face. That's assuming the guides are ok, and on non-turbo engines they normally are. I lap re-ground valves and seats together.
I use New-way cutters for the seats, and a Sioux machine for the valves. And I take as little as possible off each to achieve the results. I also grind the valve stem tips to length and then don't have to change shims. That's a method last used on Ford flathead V-8's!
So me, I'd grind and cut them again. But you could lap them and get away with it.
Rhys