alignment is required, not only will your car track down the road better but you will evenly wear your tires and new tires are not cheap - plus wear on your joints, etc.
You may also want to look into replacing or upgrading your upper strut mounts (plates), aka camber plates. These doughnuts are located on the top of the front springs, and they have bearings in them. They wear out after a long time.
If you buy the $300 camber adjustment plates you won't need the camber bolts.
Since you have to take the springs out to get to the shocks, the upper strut plates are right there. If you have more than 20k miles you may want to replace them while your in there. They will squeak or pop when they are worn out.
Choices: stock Mustang GT - $60 each motorcraft
stock Shelby GT500 (stronger than stock) - $65 each Ford Racing
maximum motorsports or steeda upper strut plates - over $300
Or do nothing and put your stockers back in, if you don't go the expensive route you'll still need to get camber bolts.
Jack
