Phil,
Clayton is correct about the round feeders, but if you are using the other feeders you should cut the lower section of the air cleaners in order to make them sorter and let space for the feeders to tilt the hood.
Anyway keep in mind that those feeders are incorrect and the result is a faux 353. The 353 model had a buterfly hood. If you want an acurate truck, go on with the round feeders to make the 359 model.
You should post some pictures, maybe someone else have overtake this issue with an other way.
Kostas.