There should be a threaded ground boss on the firewall just above the battery tray shelf. That's where the battery ground goes. Then below that, where Fred says, is another threaded ground boss. A braided cable goes from there to a starter bolt. They always use a starter bolt for motor ground because it's near main positive cable input at starter stud. A braided cable from one of those places to the frame is also necessary. None of this is cast in concrete (just in the FAM), but battery neg-motor-body-frame must have continuity.

Right is right, even if everyone is against it, and wrong is wrong, even if everyone is for it. - William Penn