if you are talking about the chambered exhaust mufflers that are offered in the moparts sponser section, they are ok as long as you don't mind loud, i used them on a project with a blown 540, needless to say i had to ad some collector baffles to make them a little more tollerable, they are on a 41 willys coupe and there is not much room under the car so i was looking for something rather sleek, the last willys i did with a blown 426 hemi i used two 12" dynomax bullit mufflers end to end inside of some 4" tubing on both sides and that was about perfect, loud but good, hope this helps.