Paul Feig posted this on his twitter with the hashtag #whattheygonnadrive. He even responded to a user who said the car looked terrible.
So it looks like he is standing firm behind this adapaptation. I for one am just happy to see they went with the classic look instead of updating it with a car that should never be the Ecto-1. Now they could still change the vehicle later on but I can only hope they do it justice.