In the early years, it was a '59 Les Paul played into a 100w Marshall amp - I don't think he used any pedals (or very few) at that point. Based on that, I'd look at some of the Marshall-style pedals, but realistically it's tough for a pedal to recreate what a LP into a 100w Marshall does.
Honestly, I like my DLS V2 in Rock mode for early ZZ tones.
Edit: DLS into an amp that's already starting to break up....
In the early years, it was a '59 Les Paul played into a 100w Marshall amp