Squeaky Steering

Steering rack bushings, spring isolators, sway bar endlinks, sway bar bushings, control arm bushings, steeing shaft joints, steering shaft firewall bushing-coupler-thingy, inner tie rod joint, outer tie rod ends. All I can think off!

Put the car up on some jack stands and move the wheel back and forth to see if you can isolate where the sound is coming from. For the steering rack atleast, look to see if it is swaying side to side when you move the steering wheel. If it is, you need to retorque the bolts, or better yet, buy some urethane or aluminum bushings (maximum motorsports = yay) and THEN re-torque to spec

+1 ^^

... and to add a few things, while its jacked up put one hand on the top of tire and your other hand on the bottom of the tire. If you can push/pull and have movement then your ball joints could be poo.

I really think your problem is dirt in your spring isolators. Reason I say that is because I had a squeek/clunk and replaced every bushing possible but I still had a slight squeek. I took my springs out and cleaned the mass amount of dirt, rocks, spider webs, etc., out of my isolators, put the springs back in and I have zero noises from the front end. That is a time consuming process so try to rule out everything else first.

Make sure your lugnuts are on tight and the only other thing I can think of is wheel bearings ... Good news is that most of the bushings that could be squeaking are relatively cheap. Bad news is that it can be a PITA to find a squeak on the front end of a Mustang. Good luck hopefully it will be something obvious.

noise while turning the wheel?

most common reasons for this is the outer tie rod ends and the rack bushings.

What Mike has said. I seen this several times.

cheap fix while it is jacked up spray white lithum [thats not spelled right] on the rod ends and see if it still squeaks, just a temp fix if you need to save up cash until you can get a permanent fix.