Either measure the old bases or the imprint of the base on the door panel to get the correct ones. Usually, the 4 doors use the shorter bases on the front and rear. The 2dr's use the longer ones on the front, but, it might also depend on the trim line of the car. Signets and Barracudas came with chromed plastic bases. Most of the other models came with colored plastic bases. The ash tray versions go in the rear....solid ones up front.