I believe I've finally found a picture of the Camaro version of the (thankfully) failed 1980s fwd GM80 program.
Comparing it to the Firebird prototype, the front axle to the base of the windshield ratio looks to be the same. In addition, the rear glass hatch between the two look identical. Though it appears that the Camaro was a little earlier in the styling development to the Firebird - That looked near production ready.
Though maybe GM could have recouped some of the development cost by releasing versions these cars
There also would have been a cousin to the Camaro and Firebird, the Oldsmobile Silhouette.