The factory manuals have all the grounds listed and diagrammed, and there are a lot of them. They are under the dash near the door posts, behind the rear seat back-rest etc as well as in the engine compartment. Near the battery tray there are some also, at least on mine.
My '85 has a ground on the left fender well, on a bracket that's made for it, just behind the jump-start box. It was not-so-good shape when I bought the car, and I replaced the bolt and nuts with stainless hardware. Grounds can sure cause a lot of problems when they get crappy.