Bucket sliders Different height

Hi:
I am working on replacing my bench with factory buckets in a 75 Swinger. You have a set from a 73-74 Duster. I have the same set.
That said, are you measuring from the very bottom to the very top of the slider? That is my guess.
Be aware the hump/hole (front left side), by the drivers door, is not where the bracket bolts through for buckets. It may be, there is a dimple about 2" to the right of that, which is lower. You can tell by looking under the floor and will see a support with a hole in it. That is where it goes. You will need (extra) spacers there to make the seat level, along with some creativity. Contact R/T specialties. They have 1/2"stock type . You will need 8.
Also, if you bolt the seat to the far left it will not line up with the Steering wheel.
It ought to be a simple changeout... Yeah right:)
Good luck...