Rear brake squeal
A somewhat common problem on SHOs (especially in the "rust belt") is the rear brakes emitting a "squealling" noise while the car is in motion.  This most likely indicates the rotors are coming in contact with the pads somehow when the brakes are NOT being applied.  The two most likely causes for this are the emergency brake not disengaging completely, and the caliper pins becoming corroded to the point they do not allow the caliper to release the pad from the rotor.

It's important to address this quickly, as your rear rotors and pads will soon destroy themselves if it's not taken care of.  Also, if your pads wear down to the rivets, metal from the pads/rotor will likely embed itself in your wheel, resulting in a permanently "dirty" looking wheel.

The slider pin can be replaced with a "kit", Ford part numbers are :

F3DZ-2B296-A  is for solid rotors - has the shorter slider pins.
E7SZ-2B296-A is for vented rotors -  has the longer pins with the hex head on them.

They both come with the dust boots, grease, etc.