Stevie had a Howard Dumble Steel String Stinger Head, amongst other amps, mostly vintage Fenders, but his tone mostly came from his technique as well as a little help from a couple of original Ibanez Tube Screamer distortion stomp boxes. Oh yeah, and he used Alembic's StratoBlasters, LOL! (Susan let that one slip a while back).
Let's face it, that guy could play a plastic toy guitar through tin cans and a string and sound good. Old Guitar Player Magazine story (from Eric Clapton): He once unintentionally humbled Clapton in an impromptu studio situation when Clapton's guitar(s) were unavailable and only a cheap, poor-playing no-name junk guitar was floating around in the studio. Clapton whined he couldn't play the thing because it was so bad as to be unplayable. Stevie gave him his guitar and he played the POS so they could jam together. Well, Stevie smoked 'ole Slow Hand on the crappo guitar, and impressed the hell out of everyone there, especially Eric. LOL!
It just goes to show you: equipment isn't everything: it takes usually a lot more than matching you favorite player's equipment to sound like him, LOL.
Similar story from Ted Nugent: he and Van Halen were on the same bill for a show. During the soundcheck, Nuge had the opportunity to try Eddie's mondo amp rig. He figured that crazy sound HAD to be due to the equipment, not Eddie's playing. He reckoned anyone that plugged into that rig should sound just like Eddie, right? Well he plugged in, had the sound man crank it up and Ted began to wail and....PRESTO!.....he sounded just like Ted Nugent did while playing through his wall of Fender Twins! LOL! Even the immodest Motor City Madman was humbled after he realized that Eddie's sound came from his FINGERS (with only a little modded-Marshall help, LOL!).