Nice! Glad to see some people on here who still love and appreciate the Kings of the Bay area!
My band toured with Exodus in 2006, it was an awesome time and I still count Gary and Lee as good friends. They even asked me to tech for them! Gary's live tone is killer, and (for the most part) could be had fairly easily. There are a few tricks and tidbits that will help you get closer, which I'd be more than happy to share with you guys here. Bear in mind that his rig may be different now, as this was almost 3 full years ago.
The most important element to Gary's guitar tone is in his guitar set-up. His fingerboards are scalloped fairly deeply, and he plays with a pretty light touch to match. Typically he has medium-low action, but with very little relief. This requires very precise fretwork, as a big part of his sound is the "crunchy" pseudo-buzz he gets from the frets but it's very easy to end up sounding buzzy and cr@ppy by going this route.
He uses a TS-9 mainly as a boost for solos, and a noise gate set pretty hard to give his sound that precise tightness for the rhythm chugging parts.
His EQ settings tend towards a scoop, but it's a far more mild scoop than they used to do. Mids usually hovered at around 3 but went higher sometimes, IIRC.
I can't remember what cabs he was using, though he used our cabinets sometimes and he sounded pretty much the same. We were using regular Marshall 1960B's, which have Celestion G12T-75's.
As far as pickups go, I remember him saying he tried a couple different models (and I faintly recall him saying he used a JB sometimes) and landed at the SH-5 though he had used EMG's in the past (Fabulous Disaster in particular). The Cold Sweat would probably land you in that general area (from what I've heard of them, I don't own any you see) and I reckon the Holy Diver would also be a good choice.
I hope that helped and didn't stray too far off-topic! :D
