[jspe]

The bottom screw holes from the white button tuners should match the spot for the Grovers. You'll still have the area above each Grover tuner showing the hole and a bit of the footprint from the previous tuners.
Before you do this, a caution...just my opinion , but with Grover tuners I've seen a Gibson acoustic headstock snap just from being knocked over on its back from standing on its side in the case. I have since avoided any type of heavy tuners and have had mine switched to the lighter white button klusen-style tuners.
If you notice now many of the "newer" Martins (and other guitars) are equipped with the nice LIGHT open back tuners....there's wisdom there IMHO.