Glass Packs
I worked for a glass pack manufacturer in the early 70's in So. Cal. Bluetone was the name of the muffler. They mere painted a metallic blue and we sold them to most west coast and Arizona muffler shops. Myself and 3 other guys made 1000 to 1500 a day depending on size.
They cost about $1.50 each to make. Wholesaled for $5.00 and retailed for $10-15.
I also did the installs and dual exhaust conversions. If you want quiet, install as far to the back of the car as possible. Install the longest mufflers and the largest outer diameter ones you can find (more packing inside).
We sold from 10" L X 2 1/2" D to 36" L X 3 1/2" D mufflers ,the long ones were quiet just like a standard muffler until the packing eventually wore out. The 10" Sounded like a trumpet.
