The standard Stingray has a drag coefficient of .30.
Its frontal area is 2.02 square meters and has a lift coefficient of .20.

Generally speaking, as you move up the Corvette model range, frontal area and drag go up and lift goes down.

This is not just true of Corvette, but virtually all performance car lines. Frontal area goes up because tires get wider and you have more aggressive aerodynamic features.
The aerodynamic aids that create downforce tend to disturb the air in such a way as to add drag.
Directing air through heat exchangers and towards brakes to cool them also creates drag.
As engines make more power, more energy needs to be dissipated in all cooling systems including coolant, oil, trans and differential lube, and in the case of charged engines, intake air.

Race cars have a lot of drag by street car standards, but they produce a lot of downforce. Race teams spend a lot of time optimizing this tradeoff for a given track.

They also have to make sure the drivers like the way the car handles. It is no different for street cars, we are always looking for ways to improve down force at the minimum drag penalty.
The Z51 option on the Stingray adds cooling content, a rear spoiler and modifies the aero panels under the nose of the car.

It's Cdx moves up to .35 but lift drops to .03, which is very close to a zero lift car.
Actually, we have tested Z51 cars with negative lift coefficients, which means those cars are producing true downforce.

The Z06, with its wider tires and flared body panels has a higher frontal area (up to about 2.1 square meters) and the standard car has drag and lift numbers similar to the Z51.

The Z06 has available Stage 2 (CFZ or CFV Carbon Fiber Ground Effects) and Stage 3 (Z07 Performance package with the large end plate on splitter and the center bridge "wicker" on the rear spoiler) aero packages that further trade drag for additional downforce. Stage 2 has a "lift" coefficient of -.152 and stage 3 is -.279.
The minus signs mean negative lift or down force.
The trade off in drag means those coefficients move from about .40 to .50.

In other words, the cars are starting to approach race car numbers. In our testing on many tracks, the improvement in corner speeds more than offsets the straight line speed loss from the higher drag.
Depending on body style, our aero packages have lift to drag ratios ranging from 2.6 to 3.6.
We consider anything over 2.0 (2 counts of lift reduction at the cost of a single count of drag) an efficient tradeoff.

You asked about front to rear down force ratios or what we call "Pitch moment".
We have strict criteria for pitch moment. The ratio needs to be held within a fairly narrow range so that the vehicle handling remains consistent.
Too much down force on the rear and the car will understeer at higher speeds.
Too much on the front and the car will oversteer. We tune all our cars to maintain neutral handling biased slightly towards understeer.

I am sharing these specifics with you quite reluctantly.
The reason is that there are many ways aero performance can be quantified. No two wind tunnels are exactly the same.

Some have moving ground planes, some do not. Many correction factors are used because none of them replicates exactly what happens in the real world.
They have finite test spaces while the world is far more open. Computation fluid dynamics (CFD) is getting so good; it is used widely and surpasses physical testing in some ways.
Bottom line is that with so many ways to predict them, numbers from one manufacturer are only roughly comparable to another
. In addition to the number of ways to measure, the cars themselves can be variable.

Small changes in standing height or pitch (relative height of the front to the rear) can have a big effect on measured numbers

Team ZR-1
True Custom Performance Tuning