Eh-hem, it's Mustang with a capital M!
Install grease fittings on the upper control arms, if they are not already there. You'll need 90 degree elbow fittings. I can't remember what size they were.
My '67 just had plugs instead of grease fittings when I bought it back in '93. It had the Mustang squeek too, and it went away after putting in the fittings and greasing it.
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1967 Mustang Convertible - 289-4V with a C4 Automatic.
1992 Bronco - 302 EFI Automatic
"When they call the roll in the Senate, the Senators do not know whether to answer "Present!" or "Not Guilty!" Theodore Roosevelt