Sorry you haven't gotten a confirmation yet. Still working on it myself, but life just keeps jumping out in front of me, making me swerve constantly!
One good bit of luck is this. If you want them to be a certain height, they can be.
For example, if you want to be at 3.5" and they turn out to be 5.5" springs, you simply remove a leaf or three. Softens up the ride even more, but might leave you without a big payload capacity. If carrying junk is in this Broncos' future.
If they turn out to be shorter than you want, you can then use a block to make up the difference. Say a 1" block, to make a 2.5" pack into a 3.5" lift.
Sure, blocks are frowned upon for hard use, or when trying to reduce axle wrap, but they do work and are quite easily "tuneable" for height.
Might not even need them initially anyway. Most of our springs are going to sit high in the rear initially. You gotta' wait for them to settle. Unless you're the impatient type, like most anyone would be in this case, and want to add some weight, or heavy driving for awhile to persuade them to settle.
So you still have options. Besides, you own the springs already! So just go the direction you really want to go, then make them work for you.
Paul