Got a 2006 GT, 55k miles, with all stock suspension, I was in a front end collision that destroyed my bumper, fenders, hood, radiator support, front control arms (which I replaced with one's off of a 05 stang), sway bar end links and tie rod ends. Those are what I've replaced so far and the rear suspension handles fine like it always has, but when im going over bumps, turns or braking, there's a couple of loud knocking noises that sounds like it is coming from the front wheel wells and I can slightly feel the knock through the floor and brake pedal. I also replaced the front brake rotors and pads but that didn't help with the noise, I found that my strut mount bolts were loose but that only helped with the slight vibrations and poor handling at around 60+ mph.

Money's a little tight right now and I can't afford to go big with some expensive Eibach or Koni etc springs and struts set up. Long story short, a friend gave me a pair of 1" Ford racing lowering springs for a real cheap price, would I be fine with putting those on OEM style replacement struts and strut mounts, and would it cause any mechanical problems to put the springs on the stock rear shocks? (not worried about comfort) until I can afford a legit set up? And would I need to do anything with my rear control arms and/or get a panhard bar if it's only an inch drop all around?

Do you guys and gals know of anything specific it might be? I still need to thoroughly check my ball joints, and possibly my engine mounts after some research. Sorry for the long post but I'm getting a little desperate.

 

You can use the springs with the rear shocks, wont hurt anything. An inch drop will only very slightly move the rear so you can get away without an adj panhard.
If you can afford it use the GT500 strut mounts (18183C), the stockers fall apart easy.
Check your ball joints but the most likely culprit for the knocking noise is the swaybar links. Torque them up crazy tight with blue Loctite (with the front end loaded).

 

On the rear, cut the top "nipple" off the bump stop. Once you put the lowering springs in it will bottom out and cause a harsh ride. Take that nipple off and you will have a much better ride.