The battery in my X is a Delco 78PG (installed by first owner). It failed my tester and seems like the correct one for our cars is the 75 Series so I bought the 75VPG which is the longer lasting one. The battery is not as long and slides around left to right with the top clamp fastened. Seems like the 78 series was wider and a more perfect fit. The 78PG is discontinued. Looking to see what everyone is going with that fits correctly in the Delco line.