This place will make a muffler that fits your pipes. Did mine here. 26" racing muffler, 3" collector. They are a custom fabricator, so you can have most any size you want:
JBA Racing
I am real pleased with how mine turned out. Was debating how large to open them up--was concerned about noise. 3" was just right. Louder than blazes when on it. Passable at idle.