I have a 70-series Big block II on my 4.3 single in dual out and it is just as loud as a V8 everyone swears they can hear me coming down the road. I paid $150 for it and had it dumped / then side exhausted / then I got bored one day and cut the side mounts off about 4" from the pipes OMG its louder than Hell

 

Thanks for all the help! Its actually really ironic, I stopped by the muffler shop with my freind and the guy said Flowmasters sounds really bad and hollow on a six cylinder. He said Magnaflow is the way to go. He said Flowmasters sound really hollow and like cars, but Magnaflow has a deeper rumble. He also said he'll install a high-flow cat, Magnaflow Single In/ Duel Out 2 1/2" all the way out the back with 3" or 3 1/2" tips.
The funny part is I went home and checked on youtube to see some videos and the Magnaflow sounds way more raspier and hollow then the Flowmaster! This is turning out to be quite funny. Ill send some links so everyone can compare.

 

Magnaflow on 4.3L Silverado:

http://http://www.youtube.com/watch?v=NdadbG33WZo

http://http://www.youtube.com/watch?v=9K81pxZDiVA


Flowmaster on 4.3L Silverado:

http://http://www.youtube.com/watch?...eature=related

http://http://www.youtube.com/watch?...eature=related

http://http://www.youtube.com/watch?v=rV-02xSrogc

http://http://www.youtube.com/watch?v=KqExnIm8Kt0

I think I know what sounds better :P