Have a look at the Ford G6 E Turbo (you might need google images, or ford.com.au) its back end looks similar to that but i think a little more shapely. Thats a pretty good job, but get rid of a little more Saab
What the front of a Pontiac should look like. Not too nuts about the rear though. Look at some of the '60's Pontiacs. Catalina, Firebird, LeMans. Maybe work a bit with that multiple lens/grid type of design.