The real 273 HP exhaust sound

In 1965 the standard 273 4 barrel system came with a straight-trough muffler system. Due to the noice problem the front muffler were changed and the exhausts took a loop in the muffler for 1966. This may have been the case for the late power pack cars that were produced. I'm not sure when they changed the muffler. I have October 1964 mufflers at home and they are straight through. I'll check the other ones.