As soon as my house closes in escrow, I am going to make the following changes to my 5.0 stang:

Conversion of rear drum brakes to rear disc, along with 3.73 rear gears( already have the rear)

Mac upper and lower rear control arms. I have just put on a pro 5.0 shifter, so this is gonna be one tight set up.

The car has 173 k miles on them. The suspension still feels tight, with a little vibration from the front, but has brand new tires. I suspect the struts since they are original. The car does not sag...but how long do springs usually last? I have the chance to buy low milage 30k miles springs from a similar mustang.

The springs will only cost me 30$, but don't want to spend that and go through the hassle of changing them if I don't have to.

I am going to replace the shocks and struts when the rear comes out, and will do the springs then if necessary.
How do I know if I need new springs?

 

Pitch the springs for new ones, not old tired ones. Cheap enough.

The suspension and the ride will feel like night and day.