In a recent jam with a band I will be sitting in with for one of their shows, I was playing slide with my R7 into a 70s master volume Silverface Twin Reverb goosed with my Keeley TS9, I was able to get some very Trucks-esque tones.
I don't know how familiar you are with Trucks' style, his tone is near impossible to nail. #1 his technique is ridiculous, I've been working on it forever and the way I play it now is still more of a Duane style. #2 his amps are modded to the balls. He uses a combo of vintage, tone tubby and Weber speakers, not to mention the Pyle Driver car audio speakers in one of his Supers. Plus his ultra treble mods. He also uses Duncans Antiquities in his main SG.
Anyway, I think a vintage silverface will get you closest. He just about only uses 10" speakers, his Super Reverbs obviously being 4x10s and when he needs more power his Super Sixes being 6x10s. I like Christian dont care much for the current Custom Vibroluxes out there. Maybe a silverface Vibrolux or better in my book a Pro Reverb (even though that uses a 2x12 speaker config). All you gotta know is that blackface/silverface type amps are gonna get you where you want. There's no way I'm nailing Trucks with my Tweed Twin, but no doubt I can get a killin' slide tone when I crank the mother up!