yes there is good spots in the trunk to put a ground. Just out of sight under the carpet there is a steel plate that covers the gastank and is bolted on. use any one of those bolt locations along the bottom. Will provide a ground without drilling any holes. I will try and find a pic explaining where I am talking about and edit this post with a pic

Edit: I found a pic which shows where existing bolts are. Under the carpet where circled is bolt locations thats where I have mine. the little circles shows bolts in the pic that could possiable be used