My 40 Tonner came with the ivory dash knobs and vent knob which were badly deteriorated. As I recall C&G or one of the vendors sold a kit which had all the knobs in it which is what I used in the truck. I would recommend installing the screen in the vent. When I first got the truck I took my wife to the local feed store to get some hay. It was a hot day and she wasn't too happy about the lack of air in the cab so I suggested that she open the vent to help cool it off. The result of that effort was the most amazing hurricane force wind that engulfed the cab with dust, wheat seed, dead insects, old gum wrappers, you name it. Not only does that screen keep things from coming into the cab it also acts as a choke plate to help control the flow of air. The expression on my wife's face after she wiped it off was priceless. Her words not so much......