Cletis, had the same problem over the years. "My" take on it is the fact the 54 has the pipes going over the rear end which can cause a " back pressure" and will them sound louder.
...that said, I had a 350 with headers in my 63 stepside awhile back with the pipes coming out the side (not going over axle) and it was fairly quite untill I stood on the gas pedal.. but even then it was not as loud as the 350, with the same mufflers, but with the tail pipes out the back. So, I think its the fact they are going over the rear "hump". I've been wrong before but this is "my findings" anyone else tried both??
