My 55 Tbird has had numerous front end mystery clicks, sqeeks and pops since I've had it. I've fixed most of them. My ball joints, tie rod ends and bushings are all new. When I got my car, I blasted and rebuild the entire front end.
Once I discovered one of the horn brackets was flexing allowing the horn to hit the grill. I practically had to take my entire front cap apart to replace the front radiator deflector. Apparently, a previous owner tried to fix overheating by torching holes in mine? What I discovered during this project is some Thunderbird metal parts are subject to flexing. As you discovered, the front radiator deflector is metal to metal with the radiator support. If all those bolts are not in place and tight, you will get all kinds of strange noises.
The exhaust system in these cars can also make strange noises. These problems normally go away after the car heats up. At this time, my car has decided to give me a break and quiet down.