Unless a mount bolt is loose I can't imagine the caliper causing your rattle.
If you're checking out the calipers, make sure to clean and lube the slide pins. If they bind up you'll end up with uneven braking or warped rotors.
You might want to check your front shock mounting. I had a rattle coming from one of the front shock lower mounts. Snugged it up and no more rattle.
I've read up a bit more on my rattle. I've concluded that it's not my brake calipers.
The noise persists when the brakes are applied lightly. I will check all rubber mounted linkages as suggested. I just bought the truck 2 weeks ago and this rattle is it's only defect.
2004 F350 FX4 off road Crew V10 auto long box 122,000 miles.
1990 F350 DRW 5 spd Diesel