SRV didn't like speaker breakup. That's why he used 200w and 300w JBL and EV speakers with his 50 watt fenders.
In fact, He didn't really like distortion at all and was always battling trying to get the sustain and thickness but with a clean tone (Hence his tendency to move towards Dumble 200watt amps later).
The trick to his tone is that He played a heavily distorted amp and a 100% clean amp all the time. Thats why his tone is so difficult for most because you simply can't nail it with only one amp. If you have a distorted amp, there is no clarity and no punch. If you only use a clean amp you get no harmonics or sustain/compression.
He also used a LOT of treble. Its a hard balance to control. FWIW, I think chasing El Macombo tone is a fool's errand. That tone relies heavily on the room along with the possibility that his amps were probably mic'd from behind (which would need a special IR capture).... but its the room vibe that gives that tone most of its sound. I bet if you look at the master recording, 80% of the tone you hear is the bleed from the other mics on stage especially his vocal mic.
Other important tricks:
•mismatched output transformers
• Solid state rectifiers (much less supply sag)
• TS9 (no famous recordings are of his 808 years...)
•*No gain on TS9 max level and tone control
•*JBL speakers ARE his tone. His tone suffered greatly when he moved to EVs in my opinion
Here are a few of my SRV tone attempts with the AXE:
FW10 Tin Pan Alley
FW7.0 Coldshot
FW7.0 Couldn't Stand Weather
FW6.0 Voodoo Chile