old school muffler questions

[Warren]

Have a 72 GMC with same exhaust on it likely 25 years or more. Pipes are not pretty but thick and solid and small, 1 7/8 I guess. 400 Small block. This will all get replaced but for now just need to do mufflers.

I want the same sound. Best as i can tell I have Thrush Turbo Mufflers but also came across Dynomax and they look the same.

Dimensions match the 17711 muffler for Thrush Turbo and 17730 for Dynomax Super Turbo. There is some extra wizardrie in the Dynomax.

There is a stamping on old mufflers I think WWO or OMM on one and WW or MM on the other. Both of them have a raised "IN" on them. Think they are 25 years old approx

Its hard to know from internet sound clips with mike placement and all kinds of variables but both the Thrush 17711 and Dynomax 17730 seem to be the same sound. Changes in which motor is in front of them changes the sound but still most sound the same.

The Muflers are aluminized and see the in and out pipe is different than pipes are now, now there is a tapered flange on the in and out of mufflers ive seen now. Short of cutting one off and opening it up is there any other way to tell for sure what a muffler is. Im wondering if those letters mean anything to anyone, Thrush did not recognize the letters but felt they were their mufflers. Then I saw the Dynomax days later and thought it could also be them.

thanks in advance,