Hold on to that vine, Tarzan, that is not as true statement, but close. The 78 Malibu has a sweep speedo, where as the rest have a dial speedo, like a round gauge. If it is a round gauge, you are in luck because Tarzan speeks with unforked tongue. But if it is a long retangular one, only 78 Malibu will fit. And before you ask, to change out the entire gauge cluster, it can be done, but you need new sending units.
Take two aspirin and call me in the AM