I called T/A Perf. And spoke with Tim on Buying the Correct TA RearEnd Girdle.Tim told me to measure center to center of the bolt@12:00 to 6:00 to get the distance. 9-3/8"spacing is a Chevy 10 Bolt. 9-3/16" spacing is a BOP 10 Bolt. I have to measure the spacing to determine which Girdle to Buy. Whether its the 1807,1807A...or the 1808 Girdle.I Thank Tim, for the info...Jay B .Britt,Jr.