As stated by dpeterson he runs two amps at a time, although he considered his Marshall Silver Jubilee the core of his sound. And his cabinets are loaded with some sort of EV
However I believe this has changed the past year or so (big surprise, the man loves his gear)
Rides the volume on the guitar allot, as stated above. However I did see a interview were he keeps it around 8 thats home for him were 10 would be home for most other people.
Something else to keep in mind guitar wise, the wiring most likely 50's style wiring, some of his guitars have it for sure. All my Pauls are 50's style.
Also on some of his Paul's he has nylon saddles on high E, B, G and I believe he also uses 11's on most of his standard tuned guitars.
I think just those things alone on the guitar side make a huge part of his sound, however not the string gauge so much.
Then the amps and of coarse the other 90% his hands.
John