Clunking noise with fox Cobra brakes

This noise is driving me nuts! When I am backing up, and I hit the brakes, I hear a clunk from the left front wheel. I have 94/95 spindles on a '90, with new '90 ball joints, bj spacers, and poly arm bushings, along with '90 kyb struts and frpp 90-93 cc plates. I have rotors from The Mustang Depot, rebuilt calipers from Advance, and pads from Apex brakes. They're kevlarmetallic Anyway, everything is tight, so its not the lca or ball joint being loose. When the wheel is off, the rotor has a little bit of rotational play, you know, around the studs. But it's gone when the wheel is tightened. All I can figure out is that the pads, not being Ford, are not sized quite right. The way it goes together, their springs are at the bottom, so when you back up and stop, they hit the caliper bracket. But I put Ford's silicone grease on there, and it didn't stop. BTW, it is very repeatable. If you're backing up, and stab the brakes a bunch of times, it will do it just about every time. If you stop real easy, you don't hear it. I don't think it makes a noise when you let off, though.

Ahh..

It turns out it is the pads/caliper bracket. I took a screwdriver and pried each caliper down, like it was stopping in reverse. There's a little bit of play on the passeneger's side, but there's more on the driver's side. This must be the noise that I am hearing. However, is there anything I can do, short of buying new pads?

I guess it depends on the pads you use, keith. Now and in the future. Silicone dielectric grease should take care of this, but ... at least I know mine's not going to come apart on 100-55 mph or anything.