Plotting Locations in Google Earth from 1960s Army Map Service Maps

I am new to using maps in my humanities reserach and I have found the maps created by the U.S. Army Map Service (AMS) in the 1960s pretty user-friendly.  When trying to plot MGRS coordinates in Google Earth, I ran into a few problems.  The free version of Google Earth does not accept MGRS coordinates, so I had to convert the coordinates to latitude and longitude using an web application.  Once I got the Lat/Lng for a location, I found that it was in the wrong place--Google Earth's  satellite view showed the location in the wrong grid square.  After quite a bit of searching, I think I have found the answer (although it may still turn out to be wrong).  At the bottom of the AMS map I was using, it said "Horizontal Datum: Indian Datum 1960."  Once I found a tool that allowed you to specify a datum, the converted coordaintes seemed to be in the correct place.