73-76 sliding calipers not sliding?

We are trying to wrap up a drum to disc brake conversion on the front of a 69 Barracuda. Been quite a few year since I worked on the mid year A body disc brakes. We got all of the necessary parts from a 73-76 donor car and purchased new rotors, pads and calipers.

My question is that once I tighten the bolts on the 2 retaining brackets the caliper is very tight. It seems to me that the caliper needs to be able to freely slide back and forth. I am pretty sure I have the retainers installed correctly. What did I do wrong?