Wouldn't you have to cut the 1/2 coil from the bottom of the spring, the part that sits in the spring saddle? I am not sure if the flat part of the spring (the one that touches the shock tower on the top in a Mustang) is always considered the bottom part, but if it is it could be confusing for the OP. Maybe I am thinking of this incorrectly, but it could be confusing for someone that does not have previous experience with this. You never cut a spring from the flat part of it, you always cut the pig tail end of it. I do agree with C9ZX that cutting a 1/2 coil is probably the best for you to drop the front, and you will not notice the difference in ride quality.
Buying springs is always a crap shoot. You think that your car rides too high, and lets say you go to the best, Eaton Detroit Spring, and order from them a 1" drop spring, you then i
7173mustangs.com.urlnstall them, and nothing happens, you still have the same ride height. That is because your factory springs have sagged a bit and what you thought was a factory ride height was in reality a little low. Eaton will exchange them at no charge, but exchanging springs is a pain. These cars rode pretty high from the factory. I just replaced my front and rear springs with correct replacement springs, and the car sits high both in the front and back. Front springs were Moog 8356's and rears were from Eaton Detroit. Have not driven it but it is high, and I do not expect it to drop much by driving it.
By cutting the spring you know that it will drop from where you were, and if 1/2 coil is not enough, you can always cut another 1/4 coil or more to get to where you want to be. Do some searches on this site and on Google and you will see what a nightmare the aftermarket drop springs can be, especially the ones that are sold for multiple year Mustangs. When they sell you a 1" lowering spring for a 1967-1973 with a small block, it just makes little sense. A 1967 car with a 289 2 barrel and no AC, or PS, and a 1973 Mustang with a 351 C with AC and PS will have a completely different ride height with the same spring. There are hundreds of pounds of difference on the front of those 2 cars. Eaton Detroit is great, but they are not cheap.