well, for those of you looking for a quiet, and i mean QUIET exhaust i belive i found the answer. the muffler installed was part #12773. i replaced my summit 'louver' style muffler with this one. it fit perfect, after a few cuts with the sawzal to get the old one out.. it still has some 'hum' to it around 2000rpms, which is where the summit muffler was ear numbing (there is some blowback at the exit clamp which im sure adds to the 'hum' a little, she'll be welded up this weekend). but no flutter and no DRONEhttp://www.dieselplace.com/forum/smileys/smiley4.gif. havn't got a chance to get any real egt readings but overall im very happy, no decrese in performance and it puts out a killer 'mac truck' whistle when you step on it. im very satisfied.

I have the same muffler, but it's shorter...like 28" I think. Just like
you said, very satisfied with the performance and low tone.