I own a '67 plexi Super Bass and have a couple different Analogman modded Tubescreamers that I occasionally use with it (Silver Mod & Brown Mod) and they sound great IMO.
A lot of guys knock Tubescreamers because they shave off too much bass, but a healthy Marshall Super Bass has such a big sonic footprint, that I find the bass loss not to be an issue. And when you get the amps volume up and bumping a bit, the bit of bass loss from a TS actually helps tighten up the sound.
In addition to the Tubescreamers I also own a Timmy and a Klon (which also sound great), but my favorite overdrive to use with my Super Bass is a Fulldrive 2.
I sold my Zendrive to buy a KoT. I haven't tried it with the Marshall yet (only with the Band-Master), but considering the KoT sucks a little of the lower frequencies, I'm guessing it will sound great with the Super Bass at loud volumes.