These are cheap thrush glasspacks on my cammed 5.3 '89 Formula. Terrible muffler, but the previous owner put them on to get by. I have LTs and a SLP Loudmouth going on it. If you are determined to go with a "glasspack" go with a Borla XR1, Dynomax bullet, Magnaflow, SLP, etc. All they are is a fiberglass stuffed straight through muffler, also the longer the muffler is, the worse they sound IMO.
Building a motor around exhaust sound is definitely the wrong way to go about it. Build a good motor, and it will sound good every time.
I said "thip thip thip" with your car, and then I tried the "thap thap thap thap". Sorry, but the "thip" fit it. Listen to your video and try saying each one. You'll find you are a thip. I don't want the thip, I want the thap. Now to change that, do you need more LSA and less duration??