Struggling to find mufflers

Hey All

I have been researching mufflers for my 68 Dart - 383 Auto that are quieter than the straight thru Cherry Bombs on it. I am adding an H Pipe in front of CB's and I can add a set of smaller sized performance mufflers in the factory position (behind trans x-member) and I have a few preferences;

quiet rumble
chambered
no drone
2.5 in/out
Prefer - centre/centre config but can use centre/offset

i had one good option but they are out of production and the local speed shop has only one - Speed FX2503AS

Each of major manufacturers sites are not helpful in finding a similar product in either aluminized or stainless.

Anyone have an idea? part number?

Thanks, Pete