the louvered style is kinda old school, some glass packs neck down in the core up to a half inch!!!! both thrush and cherrybombs are "staight through mufflers" and thrush generaly makes longer glasspacks, so if you want it loud go with cherry bombs

 

Another old school sound is the chambered mufflers like on the corvettes.
Classic Chambered Exhaust Inc. - Home Page
I am going to try them either on my 65 or my 78. Just a thought

 

Cherry bombs are a louverd core unless they recently changed their design, it's been awhile since i've had a set of cherry bombs, but whom ever manufacture's them i'd avoid any glasspack like the one on the right (louvered core) they create way too much back pressure, you're much better off buying a glasspack like the one on the left (perforated core) they create virtually zero back pressure and flow like straight pipe, thrush glasspacks are a perforated core.

 

I personally think all glasspack are the same. Varried by the length and width.

Glasspack and fart cans are internally the same. cherrybomb, thrush, summit, etc.... they are all the same. They are just packed with fiberglass.

And yes later down the road when all the stuff blows out of them they sound even better then when you first got them