Hollow Thrush Mufflers (vintage?)

Does anyone remember the aftermarket Thrush muffler model advertised in the 1970's as long lasting because it had NO fiberglass packing (just louvers, I guess). I installed them on a new 1971 383 Roadrunner and found:
a) At idle they seemed twice as load as the factory mufflers, but not too loud.
b) Cruising at 70 mph (3000 rpm) they were QUIET.
c) At full throttle they were LOUD. In fact, a friend watching (and listening) me bracket race the stock 383 at Freemont Raceway circa 1972 told me he had no problem hearing me race alongside competitors with open headers. I also used to enjoy sneaking up behind high school classmates (girls) walking to school, popping the slapstick into neutral, blipping the throttle to 5000 rpm or so, and watch them jump straight up into the air!
d) After driving the car for a couple of years with no tickets, it was sold to a friend for $2,000. (I know, stupid). The new owner soon received a ticket for excessive noise and was obligated to replace the stock mufflers.