good ground in a 97 cop crownvic

Iam working on a crown vic and i need some help :P. The stock radio harness has been cut and i followed the diagram that i got from the12volt but ive got a problem. Theres only 2 grounds and everytime i conncet them to the ground in the aftermarket harness it only comes on when the lights are on. Now i now i can just ground it to a bolt but where. I cant seem to find a bolt/ground that i can just ground the wire to thats close by the radio. Any help would be appricaited thanks.((NEsAuDiO))

yO i dont no wat to do no fuses are blown or anything but the head unit still wont work. I grounded it to the ground that the12volt told me to and thats the headlight. The unit only works when the headlighs turn on if i connect to the ground that the 12volt told me ive even just grounded to medal in the car and it still wont work i even went as far as to just run some wire to the neg terminal of the battery real qucik and it STILL wont work. I dont think its the headunit because i exchanged it for a new one and the problem still continued. Please some one hlep me thanks :)((NEsAuDiO))