He uses Mesa Boogies. The main components of that sound seem to be thick compression, OD (not distortion), and stong midrange with reduced highs.
I read a long time ago that he uses 26ms delay, and a room reverb for rhythm. And 460ms delay with hall reverb for leads.
He also uses his neck pickup a lot for solos, and a bridge humbucker on crunchy rhythm is a must.:)