Fender Jazz...Lakland makes a Joe Osborn bass, too(based on the exact Fender Jazz he used; IIRC, Lakland had the bass disassembled, measured, weighed, etc to get it perfect!).
IIRC, with the neck pickup solo'd & played with a pick.
Some interview I read long ago...Osborn said he played 90% of everything on the "A" & D" strings, somewhere between the 1st & 5th frets.
He also worked with The 5th Dimension("Let The Sun Shine/Aqaurius")