I installed hooker side's and the 4" glass pack mufflers (with the larger diameter)

Take the mufflers out.....

Sorry...someone was gonna say it....might as well be me!

Can you get chambered inserts for the pipes? Those would prolly give ya the sound you're looking for. IF this is a stock engine, tho...might be a bit tough to get a really good "rumble" out of it.....

Take them out? As in run straight pipes? That would certainly be loud, but probably not the bass I am looking for – I would imagine that resulting in a sharp pitch? No, not stock. I build an aggressive 350 with a comp cam lots of overlap and long duration, its an aggressive sounding car that people can hear coming. The volume with the glass packs is ideal but it’s a deeper bass I would like to get at this point. Chambered? Such as Sweet Thunder ? or the Classic Chamber? Do you have experience in hearing these in comparison to the super comp glass packs? What would be a reasonable expectation from making a switch to one of these over the packs ?

One other question.  What is your take on the STS - these: http://www.spiralturbobaffles.com/corvette.html

The original Corvette sidewinders had chambered pipes, and they sounded great. However....the small block cars had more of a "cackle" sound, whereas the big blocks had the deep rumble sound. Same pipes, different displacement engines....that makes a big difference in the end result, as far as sound. Big blocks rumble, small blocks scream.
I've never done a side by side comparison of different muffler systems myself, but usually, a big cam like you have would normally give a deeper tone thru chambered pipes.

I have the chambered mufflers from sweet thunder and they have the deep sound I was looking for. They are not in sidepipes though, but they do make the 350 sound good.