Thanks Mark. I started with a standard sized air filter but could not quite clear the hood despite my best efforts to get the engine low in chassis. The 9 in. filter benefits the hood opening I carved for the hood scoop. I'm doing csx2196 Sebring spec (The Turd) which was a leaf spring car with a H&M 427 thrown in and pretty rough fender flares to widen the track. The one you want to do is the heavily re-engineered csx 2196 in Nassau specs with the clamshell front and rear bodywork (Flip Flop). BIG challenge, perfect for you!