Factory AM antenna comes from the antenna being mounted on the passenger side cowl piece. One of the aftermarket places sells a template. Although, i used it and it's a little off. Best to use or find an original and make you own template. The antenna wire goes and enters the cab near a body seam under the side cowl which is about a nickel/quarter size and this should have a grommet of appropriate size. Maybe look on the inside of the truck under the dash top? Possibly it was repaired or filled in on the outside by a previous owner.