If your car does not seem to be sitting at the right height due to tired coil springs, etc., you can check the suspension standing height per shop manual in the Chassis Suspension Chapter 4.
For the front (1963 &1964 Shop Manual page 4-15, Fig 4-21), measure from front rear lower control arm flange up to the center of the hole in the frame as seen in the shop manual illustration. Correct Standing Height Ranges are listed by body style on page 4-32 in ship manual and seen at top.
For the rear (1963 & 1964 Shop Manual page 4-15 Fig 4-22), measure distance from top of rear axle housing straight up to lower underside surface of the frame. . Correct Standing Height Ranges are listed by body style on page 4-32 in ship manual and seen at top.
A coil spring with over a thousand pounds on it for 50 year is going to compress. Metal becomes fatigued and even thought these are stout coil springs they will compress.
Also, keep in mind that there were many variations on the springs depending on whether or body style and if you had regular or HD springs. For 1964 you had 7 different springs (4 regular and 3 HD, and 5 on the rear (3 regular and 2 HD) and 2 variations of leaf springs on the commercial chassis leaf springs.
NOTE: Comparing the height of uninstalled springs, especially New HD springs and old regular springs is basically Meaningless! You can take a new HD spring and sit next to a comparable regular spring, both on level ground and uncompressed, and the HD spring will sit or so lower than the tired old regular spring but when you go to install in the car will force the car up to the proper height. When I first ordered my CDV HD springs from Kanter I thought I had royally messed up when I compared the two, but once I installed the spring I was greatly relieved.
For reference the springs are listed on page 4-32 and 4-33 in the 1964 Cadillac Shop manual.
Here are scans from those pages:
Now included on our help page - www.help.6364cadillac.com
Bumping this up since there is a lot of coil spring discussion on the forum. There were 7 front and 7 rear coil springs used originally depending on body style and regular or HD spring used. This is on the Help Page under: