Flowmaster "50-series big block" mufflers for quiet exhaust?

[Michael]

For the folks running lower-rpm, higher displacement naturally aspirated engines (say, 400 cubic inch and above), what have been your strategy to get reasonably quiet exhaust that isn't too restrictive?  I stumbled across Flowmaster's purportedly quietest series of mufflers: https://www.flowmastermufflers.com/products/exhaust/mufflers/street_chambered_mufflers/50_series_big_block/ .  These would, coincidently, go behind a big block (Chevy).  Muffler size isn't an issue, since my fuel tank is removed (S30) and there's a fuel cell in the hatchback area.

 

My question is about simultaneously quieting the exhaust and keeping backpressure to a minimum.  This would be dual exhaust, of course, with a conventional crossover pipe, and headers (for the moment, block huggers).

[Brad-ManQ45]

Unless you are running high compression, I'd look elsewhere.  These chambered mufflers rely on pressure waves to cancel sound.  Lower compression = less sound cancellation.  I had a Flowmaster put on my '83ZXT against my wishes by the local Z shop back in '95 when I had to replace my turbo with a bigger one and had a 3" mandrel bent system with cat put in - because the owner had one in his DYNOED 600 HP 280ZX.  I drove it home to try it not expecting much and it DRONED at set speed and was loud.  I was back the next day and had them put in a DynoMax Ultra Flo center in/out oval canister muffler.

 

Not only was it a bit quieter, it didn't drone and the car even spooled up quicker.  The owner humbly said he'd learned something from a computer nerd.