There's an article and 1988 interview with SRV in the latest Guitar Player that includes some details about his gear. Summarising what he says:
Used to use two Fender Vibroverbs, two Super Reverbs and a Dumble - that's the one that's onstage right now. My favorite rig right now is an old Marshall Major, the PA top with four inputs.
There's quite a lot more details. Well worth a read.