I have a 71 Malibu, all stock. I suspect the springs are sagging and am going to change them out but am looking for a certain look. Does anyone know the original dimension from the center of the rim to the fender opening ? This will allow me to determine the amount of spring sagging.

Robert in the service manual it lists the dimension of the frame to the ground in several places. A lot of the springs available will improve the ride, but buying the "correct application" will not necessarily get you the stock height. I replaced my sagging springs with stock small block with A/C and it made the ride better but did not restore to stock height. Find a car with the stance you like and ask the owner what springs were installed.

Another option is a coil over shock adjustable set up. Having had the problems with the 72 the Nova is getting a QA1 coil over front suspension. It bolts into the stock lower arm and allows the ride height to be adjusted to where it looks good.
It arrived last week and looks great. It is also going to be much easier to install then the stock spring and shock arrangement.