You could drill and tap the gimbal ring but make sure the location you pick will not interfere with how the drive tilts and turns. Really thought that wire is only for corrosion it is not needed for any type of electrical circuit that operates electrical items on the engine. Unless you are using this boat in salt or really polluted water and leave the boat in the water all the time and you want your corrosion protection to be perfect I would leave the wire off. I am in the great lakes (fresh water) and lots of boats are missing this wire because the stainless screw will corroded into the aluminum bell and breaks off when removed to do a boot job. I would leave it off and not worry about it. Also making a mess of the gimbal ring by drilling and tapping it wrong could create an expensive problem or be a safety risk.