So can I use Harley grips that have throttle hookups and just not use them? My local Metric dealer said most any Harley push/pull throttle grip would work. Only thing that could be an issue would be the throttle housing opening not being large enough. In that case, just filing it down some would fix it.

The blue is the grip, the red is the sleeve which includes the slots for the throttle cables. You either get grips that do not have slots for push/pull throttle and glue it to the right side on the sleeve [easy mod] or get grips that
do have the slots and remove your existing sleeve as well [harder mod]. Grips that include the slots for the cables need to move freely in the groove provided in the switch housing that covers and guides the throttle cables so if you're going that route you need to be sure that the size of the new right grip will fit the switch housing. It's really easier (IMHO) to replace the grips with new grips that will fit over the sleeve and not have to dink with removing the sleeve.