John, I have sold it now, but I'm sure the adjustment was under the TRC at the head. Loved the bass, hated the horseshoe getting in the way. Because it was magnetic I could not remove the shoe covers. I now play an 'S' and it is perfect for me.
I also play an S, an '81 4003 and the only thing I don't like about it is the truss rod system, and the fat upper horn. I actually like the pickup cover and have replaced it on a few Ricks I've had.