Yes, I've done it on a 63, and my 67, before going with air bags. You can test this by cutting your stock springs about 1/2 a coil for every inch to see how it will look. 3" drop in the front is not recommended unless you like riding on the bump stops, it will bottom out on every little bump. Also make sure you get some good shocks, designed for slammed car.
Suspension travel on your car is fully extended 13.42" and fully compressed you get 8.56" for a difference of 4.86" inches of travel. If you pull three inches out of that you are going to be riding on the bump stop or trying to pull the piston out of your shock.
If you have any doubt of this for free you can pull out your spring after marking it three inches above the pigtail in the spring socket (or below as I can not recall which end of the spring has the pig tail and which is open). Cut at the mark and reinstall your three inch lowering springs. Drive it around for a while. I will bet you will soon give up on this idea.
Lowered cars are a car show thing. Great for selling magazines and getting Ooohs and Aaaahs at a car show, but you will need a trailer to get your car there. No one ever mentions this in a car magazine write up.
If you want the frame dragging the ground you have to lower it from ride height by way of hydraulics, or give up on the idea of driving the car. The reason air bags are expensive (states side you can steal a full air bag system out of a Lincoln Continental Mark whatever, or an old Peugeot Citroen as both used a hydraulic suspension from the factory) is because it is the cheapest way to lower a car and still be able to drive it.
I've already got some better shortened shocks ready to go in. Im not looking to drag the car along the road while driving. Just trying to make it look a little better and removing some of the cloud like feel when going round corners.
Perhaps i might start with a 1 inch drop spring and 2 in the rear to level it