Hi Mgirouard3,
I remember reading in one of the many bass magazines that JPJ actually played his bass through a Leslie on Heartbreaker, not sure what he used for the overdrive/distortion tho...you can hear the Leslie spinning after Page's guitar solo when the bass comes back in, its a very slow tremolo/vibrato effect, I had always wondered what was going on there, after I read that it all made sense, if you listen to the Ocean you can hear a telephone ringing in the bridge just before the Naa Naa vocal part, just another odd thing LZ did.
I use a Tube Works Blue Tube pedal ( which is actually made for bass/ keyboards) or a ART SGX Nitro for overdrive/distortion, although I don't use OD/Dist that much and I'm not always playing my Alembic...........both units work well with the different basses I use.
B.