On my '65, I'm using long tube headers with 1.75 pipes all the way out to the bumper. I've got 24" glasspacks under the bed, just forward of the coil springs. No x-over, just straight pipes coming off the headers. Normal driving isn't loud but, if I romp on the accelerator it gets pretty loud. I actually love the sound when the secondaries open up . I have a hard time staying off the gas 'cause it sounds cool which of course gets expensive.
If you want all quiet, all the time then yeah, look into the Walker:
quiet mufflers -David