For locator pins I suggest using steel bushings in the table.
Also if you are going to be taking the vises off frequently I suggest drilling and tapping holes on the bolt pattern that Kurt vise and Helicoil the threads. The aluminum thread will fatigue and strip fairly soon, not to mention if you wrench too hard you will strip it.
On my GR510 I tapped the table 9/16" NF on a 4" grid then screwed in steel inserts with a 3/8-16 internal thread. The inserts have a flange that fits in a shallow counterbore around the 9/16" thread and are locked in with small setscrews. This way damaged inserts can be removed and replaced.