I believe Trucks plays BF Super
Reverbs. Wasn't some of his gear ripped off a couple years ago, and it included 1 or 2 SR's?
Jerry circa early '69, almost all of what he is using just the guitar, its tone controls, and his cranked Twins...
However I still believe that a secret weapon was employed on those short "harshly glistening" passages that occurred for approximately 1 minute each somewhere in the depths of the Dark Stars of that era (on 2/27/69/Live Dead its 14:00-15:00 approx). It is one of the most GONZO sounds I've ever heard JG get- so oddly squeezed and bursting with harmonic content. Some say it's from picking behind
the bridge, but I'll eat my words when I hear someone reproduce the sound convincingly in a posted clip.
I've come closest (not having an actual SG) using my Schecter C-1 into an octave-up fuzz (Foxrox Octron), into a wah sitting near the top of its range(bandpass filter). My hypothesis is that someone on the GD technical team had built a homemade effect box combining an Octavia-like circuit with a simple BP filter and voila: Insect Fear. It may have been too large a device to place onstage or Jerry didn't (yet) want to have any pedals... or it sucked tone and needed to be physically patched in and out. I think it's very believable that a crew member (or "human switch" as Scully describes Bob Matthews operating the leslie) stood at the ready to engage and disengage the effect at a signal from Jerry.