make 225 sound better?

Here are some Ideas..
None of them really have anything to do with the exhaust, but that's how we hear it.
Proper Cam / Head / Compression choices that live in harmony with one another.

Your Slant will sound better when it is not stock no matter what exhaust you put under it. I no longer use shops. I build it all myself.

This one is not really an exhaust comparison, but you get the Idea..


Here are Stock Replacement Mufflers on a proper dual exhaust Slant 6:


Running on the Back of the Dragon:


and just for fun! - with no exhaust really.