When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
When I installed my amp, I used a self tapping screw and drilled into a pice of metal close to the amp.. I have also in the past, just found a bolt and nut that was holding something to any metal part of the car. that was near the amp.
Try to scrape away some of the paint too, it makes for a better ground. AND if you do use a self tapping screw...make sure it's short and won't hit anything if it goes through the body (i.e. gas tank ) peace