Well here's what I've been able to find in answer to Mule's question.
According to an interview Phil did with Bass Player magazine, June and July of 2000, at some point he went back to basics and played a Music Man bass for a while. Then around '81 he heard that Modulus was making a fiber-graphite, neck-through-body 6-string bass, and he's played Modulus ever since.
In a 1982 article for Musician magazine, David Gans says after years of using sophisticated, custom-made basses, Lesh recently turned to simpler instruments -- but only temporarily. A chance encounter with a '57 Jazz bass caused him to shelve his Doug Irwin (a twin to Garcia's six-string), and he subsequently switched to a new G&L bass. But then he writes that the G&L will soon be replaced by Lesh's dream bass. Here he's talking about a six string that will incorporate a filter developed by Lesh and Alembic for the modified Guild Starfire II that Lesh played from 1971 to 1974.
Edwin Hurwitz, a member of our forum, in a bio piece for the Philzone.com, writes the short story is this: Phil started out on a Gibson EB0, then moved to a Fender Jazz Bass which he used until '68. After that he played a not very modified Guild Starfire (preamps and some magnet changes in the pickups) through late '69 or so (Live Dead is a great example of this sound). The next bass was a heavily modified Gibson EB3 (I think it was a long instrument) which had new hardware, preamps and Guild single coil pickups installed by Alembic. This bass can be heard on Skullf*** and other recordings of the time (DP from the Fillmore '70 show is an excellent example of this instrument). This instrument was stolen (anybody out there seen it?) and was followed by the Starfire, but this time it had it's front removed and replaced with all new pickups and electronics, including an Alembic superfilter and quadraphonic pickup. The headstock was also replaced. It was called the Godfather. This is the bass heard on Europe '72 and in a lot of ways my favorite of Phil's various sounds. It can be seen at Alembic's website. In '73 he received his first Alembic 4 string bass that was also quite an instrument, it was also quad and is seen in the Grateful Dead movie. It interfaced quite well with the Wall of Sound. This bass was followed by a Doug Irwin and then a G&L as well as Flirtations with an old Fender Jazz. Finally, in the early 80s he got his first Modulus 6 string.
