You could do a grill block on the inside or the outside of the grill. On my Prius and Jetta Wagon I used black duct tape on the black plastic grill to block off sections of grill and reduce airflow. It is an easy way to test to see how much can be blocked without causing overheating problems. Some people use black foam pipe insulation zip tied to the grill for the same effect. In older days when radiators were easier to get to people would just use a piece of cardboard placed between the grill and radiator to block airflow in the winter so engines would heat up faster. There are lots of ways to do it.
Or you could do the reverse - buy a Spark EV grill that is completely blocked and start adding holes to it.
EV grill
ICE grill
