FYI, they go to the Spirits maybe for more impact control. Having been under both I can firmly say the unibody on the AMC is quite a bit more robust. Pinto stuff uses thinner metal in their unibody, the thinner smaller pieces are less strong. Look at the crossmembers.. ....... The AMC unibody underneath is virtually the same except in vehicle width as used on bigger boat anchors they made, not so on Pinto/Mustang.