Are the brakes/steering/suspension stock right now?
Are you planning on keeping it 4 lug, or going 5 lug?
If it were me, I'd just find a donor 91-93ish Mustang GT and swipe the steering rack, spindles, front brakes, sway bar, etc... out of it, and bolt it right into the 79. If you have stock suspension/brakes/steering, it will feel like a new car with the later years Fox parts. As far as struts and springs, that is totally dependent on your plans as far as lowering the car or not, and how deep your wallet is. You want to do the struts and springs at the same time, but you might not want to use either yours or the ones from a donor. ???
I know you were talking about struts and springs for the most part, but I was pointing out the fact that if you still have the 79 steering/suspension/brakes under your car, you have some really weak/out of date tech going on there.
We put all these things from a donor 93 GT into my son's 81 Fairmont, and it was an incredible difference in handling. Your 79 should have the same parts as the 81 Fairmont had stock, even the 9" front discs...
1987 Mustang GT [Mine] 1981 Fairmont Futura [Son #1] 1994 Mustang GT [Son #2] I am the mechanic on all of 'em...