The Dynomax Super Turbos are not the same as the original Chrysler mufflers internally - they flow better than the OE ones I would bet on. The correct ones for the A & B-Bodies were 20" long bodies, & offset entry / center out. These design Super Turbos flow in either direction also. Dynomax called the 17748 a "Hemi" muffler - because of the configuration. A 3" version of this is #17769. This is also a 20" long body, but a larger oval body - 5.5" x 11". The center section of the Super Turbos are wrapped with a fiberglass blanket for sound absorption, but this will break-down & dissipate fairly quickly so the mufflers will get louder over time. The 3" version will get REALLY loud - I have a buddy that has the 16" bodied ones on a 440-6 Challenger & they sounded great when the system was new, but after a couple of summers the exhaust got ridiculously loud. Car needs resonators now to be tolerable - he still has not installed any & I've offered to make some for him. The Super Turbos look like stock mufflers - they have spun-locked heads, not welded construction. They have large diameter internal flow tubes, unlike OE mufflers that downsize internally. They also have a lifetime warranty - so keep your receipt. I would use the Dynomax instead of vintage OE mufflers any day.