DO NOT use polyurethane bushings on your front end, you will end up switching back to rubber i promise you. If you decide to use polyurethane for some reason DO NOT use them on the strut rods. People are literally breaking strut rods on vintage stangs because the poly bushing is too rigid.
Look into a new set of upper and lower control arms, roller spring perches, coil springs, shocks of your choice, sway bar, export brace, monte carlo bar, roller idler arm, relocate your upper control arms (also called a shelby drop).
Front and rear suspension go hand in hand, you don't want to do one and not the other. Look into rear leaf springs, rear shocks, sub frame connectors, rear sway bar (maybe),and traction bars (if you want them).
As far as the sway bars go, you will want a 1" sway in the front and if you put one in the back you will want a 3/4" to match the 1" bar in the front. If this car will see track time then you will probably find (after spinning out a few times) that you will want to take the rear bar out.
If you are looking for a firm ride that sits at a nice ride height you will be looking for:
Sub frame connectors (a MUST for vintage mustang handling-do not bolt them in, weld them in)
Shelby drop on your upper control arms (great improvement)
1" sway bar in the front, no bar in the rear
Roller spring perches
Monte carlo bar
Export brace (goes hand in hand with the monte carlo bar)
620 1" drop coil springs
KYB gas-a-just shocks front and rear
Mid eye rear leaf springs
If you don't have at least front disc brakes, now is the time
Here is a place to start: www.opentrackerracingproducts.com
The mustang II front end is an option but in my opinion it is $ that you don't need to spend. A lot can be done with your current set up to make it ride and handle MUCH better than it currently does