Hardware screen, 1/4" grid, about $1 new, tilted and mounted at an angle to air flow. Sometimes just cut a little longer than needed and curved with downward pressure. It stops rocks, clag and small birds.
Secure it with Ty wraps, rivets or the spring pressure of a curved piece held in place by the confines of the mounting area. Sometimes secured with Ty wraps to any spot available, doesn't need a complicated frame support. Cut off the exposed wire ends. You'll know why the first time you try to remove it.
Used forever, never lost a radiator or an oil cooler, when they were mounted about 2" or more behind the screen.
Tested to a little more than 190 mph... That's all I could do at Daytona.