Glasspacks?

[66StangGuy]

a friend of mine said that he had some glasspacks laying around somewhere and he said he would look for them for me. i was wondering.... iv heard that glasspacks cause you to lose power. im assuming they are very restrictive and create a lot of backpressure. but i still think that whey would be fun to have for cruse nights. are glasspacks louder then 1 chamber flowmasters? what would you compare them to sounding like. How much are these worth? Im thinking of building and exhause system for these. just the 3 bolt collector piece that bolts to the headers and then to a 2 or 3 foot pipe then the glasspacks this way i can switch back and forth easily. thanks in advance.