[6d7gto]

Is your trunk floor pan original? If yes, it should have a 1 3/8" hole a few inches to the right of center when looking down from the center of the tail panel (where the tail panel comes to a slight point). The end of the bracket's right post lines up almost exactly to the middle of that hole which will get you in the ballpark.

If no hole is there for reference, here are a few measurements you might be able to use instead. From the left side of car, I get a distance of 7 3/8" from the tail panel's squared off edge (where the date code is stamped) to the latch bracket's left post. The right side is 6 3/16".