[SCOTI]

Originally Posted by sick472

I just put these on my 72 that sports a 350ish HP 400 (Pontiac motor)...

Dynomax Performance 17749 - Dynomax Super Turbo Mufflers, from Summit Racing (67$)...

https://www.summitracing.com/parts/WLK-17749

These 20" case length mufflers have the offset inlet and outlet and fit nicely where the General originally put them. They should compare very closely to the Walkers that Mike suggests. They are quiet and have great reviews for not being restrictive. The only complaint I have is that my exhaust system does have a short drone at about 2500 rpm in second gear (35 mph), not at highway speeds in third however. I think this is due to the pipes just off the manifold having to be 2-1/4" diameter to fit the manifolds. These pipes necks up to 2-1/2" within 2 feet of the motor and continue out the back at 2-1/2". I'm not very versed on exhaust systems, so the drone may be due to something else, but I doubt that it's on the mufflers. My duals are traditional and do not have the X or H pipe.

x2 on these mufflers.

I have the 3" versions on my Squarebody dually based off of internet research of muffler flow vs. sound testing. The testing was w/2.5" units but these mufflers tested almost @ the top spot for flow (straight-thru exhaust & a race only muffler ahead in flow) & were the most quiet after a stock muffler.

My set-up is:

461bbc w/true dual set-up.
1.75" full length car headers w/a 3" collector
3" head pipes to 3" H pipe into 3" In/Out mufflers
3" tubing out of the mufflers immediately reduces to 2.5" tubing
2.5" tail-pipes to the rear bumper

It's stockish quiet until my foot is into the throttle.
No drone.