Here's what you do;
- You can either remove the front suspension lower control arm from the vehicle, or remove the front strut and spindle from the car.
- If the lower control arm was removed from the vehicle, position the lower control arm in a vise so that the ball joint is easy to service.
- Using a large C-clamp and adapters, (you'll need some specialty tools for balljoints which I'll list at the end) carefully press the old ball joint out of the lower control arm.
- Leave the protective cover in place to protect the new ball joint seal while you install it. It may be necessary to cut off the end of the cover to allow it to pass through the receiving cup adapter tool.
- Press the new ball joint into the lower control arm until it's fully seated. You'll need the following tools and keep in mind they don't have to be made by Ford but it's what I used (Ford's Ball Joint Replacer D89P-3010-B, Cup D84P-3395-A4 and C-Frame T74P-4635C)
1984 Mustang 331 stroker
1990 Mustang 5.0L convertible