Is it just distortion? It almost sounds like he's got his mic plugged into a cheap practice amp.
Fender Telecaster w/ Dual Gibson Humbuckers
Ovation Celebrity Acoustic/Electric
Fender Frontman 212R
Old Too Young (Folk/Bluegrass/Punk)
The Orange Line (Stoner Metal/Punk/Alternative)
You can replicate with EQ and distortion.
In studio he does sing thru' a small solid state peavey amp or thru' Avalon VT-737sp to get the same sound.