Ok. Here is what I found.
You might already know some of this if you have your trunk off.
The longer brackets with the little step in them are 9 11/16" long, from the bolt holes, center to center. They are about 1/8" thick and 5/8" wide. The little steps are about 1/2 " total outside to outside. The spacers they they mount to the chrome rails with are 1" tall. It looks like the steps are there to clear the chrome rails toward the back where they taper down.
The u-shaped brackets that hold the CB to the long brackets are 5 1/8" long from the bolt holes, center to center. The u-shape is 1 1/2" deep. And they are 1/8" thick and1/2" wide.
I think you are going to have to modify the measurements though, because the CB is 6" long (not including the wires) x 4 1/2" wide and 1 1/2" thick. But the radio is 5 1/2" long( not inc the wires) x 5 9/16" wide and 1 3/8" thick.
Plus I don't know how you are going to lengthen the 9 wires that go to the radio!!!
Here are a couple pics.



