If you want a compact center in/out muffler that muffles (but isn't 'too quiet') the Hushpower IIs are a nice piece.
I've heard them on (and off, for frame of reference) of a V8 Flathead Ford.
Not the same sound as a 6, but it was qieter, without any of the 'gurgle' that some mufflers give. Had a throaty rasp to (with them on, and more so with them off).
That's the only experience I have with them, but I'm contemplating a set for a 6 powered car we have, going to have to try them sometime.
